Episode 4: Results at 10 months later
Nope, my experiment of adding 1/4 cup boiled linseed oil and 1/4 cup mineral spirits to a gallon of Behr semi-transparent oil-based stain did not work as well as I'd hoped. Most of the deck looks okay, but numerous spots are peeling. The fact that it's spotty suggests that the problem may be poor adhesion. The peeling film brushes off easily. But I suspect there will be more peeling with time.
I'll do some scrubbing and maybe touch up some spots with the plain stain just to keep the redwood color uniform, but do nothing else this year. I'll see how it looks next year and decide whether it will need sanding before the next regular stain application. And I'll try Cabot's next.