I struggled with this as well (<http://tinyurl.com/675gf ). I ended up using Jeff Gorman's suggestion (<http://www.amgron.clara.net/planingpoints/edgeplaning/squareedgeindex.htm ) . It works very well if you should want to give it a try.
Although certainly not an "old" hand at it now, I have flattened quite a lot of very rough stock by hand, typically 10" wide stuff. Sometimes I thickness small pieces by hand just for the pleasure of it too. If you are going to do this much, a scrub plane is really really really handy. You might be able to get one cheap used, or get ECE woody, or get a really crappy #4/5 (used or Home Depot junk) and put a *heavy* camber on the blade and open up the throat a mile. This will make the heavy chores surprisingly fast and easy. You really want to do this, honest. Use that crappy grinder of yours. It's a scrub plane, it doesn't have to be perfect (hell, mine currently has a pretty good nick out of the blade...)