Greg - the only way you can get the finish you want is to practice. Too fe w people want to put the time in the craft of finishing to do it well. It is not rocket science by any means, and I try to advocate for the easiest m ethods possible to take the mystery out of good finishing.
That being said, I do this as part of my job as a contractor. I have to gu arantee my finishes and their application, as well as long term appearance. So my thoughts may not align with many folks. There are many that like t he actual application, reapplication, and then the same thing over and over and over to build finishes. If that is what someone wants to do, so be it . I look for appearance, utility, speed and repeatability. And of course, a finish I can warrant against defects.
There is a lot to learn to be a great finisher, a process I don't believe e ver ends. However, one can be a good finisher, a competent finisher and ce rtainly a few rungs above your contemporaries with some practice and dilige nce. As I said before, like any craft finishing takes practice.
THAT being said, don't practice on your projects. Take those old scraps an d odds and ends and make a lab of tests, keeping good notes. Try different finishes, different techniques, different products, etc. on the stuff that will go into your next bonfire or trash pickup. When I am challenged with a new product or want to find its boundaries, I like to buy door skins or damaged birch (or any hardwood plywood) to practice on. I measure off squa res with blue painter's tape and number the squares and keep notes on the f inish.
Using that method, you can try plain BLO next to urethane or varnish for co mparison. You can compare different products easily as well as different b rands. This is a great way to compare appearance, re-coat times, as well a s the number of coats needed to get the appearance you want. Additionally, you can have the hands on experience of testing out abrasion resistance.
Also, you can observe how the different ingredients and finishes work on wo od. For example, eventually (unless there is a reaction in a home brew) BL O will dry out. It leaves a very dark color to most woods and will obscure the grain in something like American (NOT French) black walnut altogether. BLO is "boiled linseed oil" which has not been boiled at all. It is an a gricultural product derived from the flax seed, and is squeezed out, filter ed and has metallic driers mixed in to dry it. So it is one kind of oil. Tung is different. The good stuff is 100% tung oil from the nut, and has m uch less amber hue (flax seeds are brown so the color of the oil in a prono unced amber) but has not driers in it. Eventually it will air cure and dry up, but for it to be used as an ingredient for finishing all manner of che micals and processes are used to make it workable. When I belonged to a pr ofessional finisher's forum, it was discovered and well documented by one o f the crew that a large study revealed there was less than 2% tung nut oil was in the can. The manufacturer defended itself by saying that it was tun g oil "FINISH", not tung oil for finishing.
The point of that is that there is no regulation on any of the finishing pr oducts we commonly see except by the govt. to monitor the VOC and metallic content. They can call their products pretty much anything the want.
dadiOH is absolutely right about the appearance of BLO, varnishes and even urethanes. They all add an amber hue to the wood, which is a by product of the oils used to make the finish. These oils tend to darken over time unt il some will turn very yellow. Personally, even though I can buy any finis h I want I have found that my clients respond well to woods finished with M inwax poly as it seems to give just the right "warmth" (read: amber hue) th ey want on their clear finished work. I have found Minwax urethane easy to work with, remarkably consistent in use, and my clients love its durabilit y. Too pedestrian for most "woodworkers", it is a solid performer for me a nd my clients.
I do not like wipe on finishes. Too much effort for the end product. But. .. they have a place. WATCO is a favorite here, and it is nothing more tha n a high quality, super thin long oil urethane. It is as easy to put on as wiping the wood. A few thin coats look nice and with the right coloration can give your project the appearance of a hand rubbed finish. It takes a long time to build up to a protective finish, but it might be your cup of t ea.
One last thing. If you are looking for a non-yellowing finish, try one of the new water based urethanes. I would strongly advise you not to use big box stores products such as Olympic, Varathane (they make a great oil poly, though), Minwax, or anything else you find there. Their products have the earmark of a bad waterborne finish, and that is chromatic reflectivity. Y ou can see a blue hue in different lights. Not acceptable.
Go to a real paint store like Sherwin Williams, Benjamin Moore, etc. and tr y their products or something like an ML Cambell water based products. All make excellent products for clear sealing purpose and are well used and ac cepted in the professional finishing industry as solid performers.
Were I in your shoes, I would go to the half price book store or check Amaz on for book by Bob Flexnor and a couple of others. Flexnor's books are exc ellent, and I like Jeff Jewitt's as well. Occasionally, you can find other gems from lesser known authors about furniture finishing/refinishing, and they might have just what you are looking for in them. I have more books o n finishing than I have on woodworking!
I wanted to take the time to type this out as I like helping someone that w ants to learn. Most folks don't, they are too smart for that. But if you come to this venue there are a lot of smart folks as you have seen, ready t o help. Many have learned what they know as many of us have, by using tria l and error as well as from one another. No doubt if you get involved in a nother project there will be plenty of folks here ready to help.
Robert