This is a scan of the most relevant Chapter of the Surface Coatings Text book of the Australian Oil and Color Chemist's association. I hope you'll find it is reasonable introduction. It's definitely not the whole story, so if anyone wants to take things further, please come back to me at my home email address- firstname.lastname@example.org
I'll be happy to feed through any info I can on specific questions.
I'll probably still try and talk you out of actually doing this sort of stuff at home, as you are dealing with flammable materials at dangerously high temperatures...
One thing that may not be clear in the chapter above is the difference between a varnish and the various simple oil media. Varnishes are made by reacting various oils and resins together. Spar varnish is an example; it contains a phenolic resin to give it hardness and good drying properties. Boiled, stand, bodied, blown and sparged oils are all names for the product of a different process where an oil (such as linseed oil) is heated to a high temperature without any other resins. At high temperature, the oil polymerizes with itself. When used as a coating this gives a tougher, faster during film than the 'raw' oil would give.