Sitka, Who said start with a small bottle, like 4 oz., of 50/50 spar varnish/drying oil and top it off with more oil after every application? Was that you? Pretty much Tru-Oil, no?
Yes, it is a common quick finish for me to use a new 4oz container of Spar Varnish and top it off with oil as I go... I never start with a 50/50 mix, but the end result is probably well over 50% oil. I slather the finish on and wait before wiping, so I use plenty.
TruOil is a proprietary blend and hard to know exactly what they use, but it has lots of the same resins commonly used in spar varnishes and very similar to the final total assay. However it gives the advantage (over TruOil) in giving resins in the base coat where it will do the most good and oils on the surface where it will produce the nicest finish.
Where I use TruOil over an epoxy base coat it works very well on myrtle... for some reason I have found the combination to work extremely well there. Pretty much to the exclusion of every other finish there. However, on walnuts I have found it is good, but I like other combinations, though I often (almost always) put a single coat of TruOil over epoxy and different oil finishes over that. I hate to admit I do not have a sound basis to justify it. But, I "feel" the TruOil makes a great binder coat between epoxy and oil. That is NOT based on any science or testing, but it makes me feel better doing it.
I have done many test boards with it and never really saw any difference or reason for it, but it makes me feel good...
