Re: What is the best way to apply varnish to wood?
For spar varnish there really is no substitute for a really nice natural bristle brush... One of the expensive ones. There is a REAL difference in the end product. I find that foam brushes tend to introduce bubbles.
Re: What is the best way to apply varnish to wood?
This B Truth ^^^^. If you really want it to last, lay down two coats of epoxy first, then 4-6 coats of spar varnish for the UV protection. It will look good for Years to come. TIP: If you get bubbles, a heat gun or hair drier or even a Propane torch waved over the surface will help get the bubbles out and level the surface, IF you are on a Horizontal surface.
Re: What is the best way to apply varnish to wood?
Like what was suggested above, my pref is for a combo of clear epoxy for a base covered by a minimum of 2 coats of a quality spar varnish (personally I like Pettit but Epifanes is excellent as well). As far as application a badger brush is best for the varnish; I have not had good results with rolling/tipping. Spraying works as well but you'll have to do more coats as the film thickness is less. Same thing for a foam brush. It gives a smooth coat but it's much thinner than using a badger brush.
If you're getting bubbles it's probably from over working with the brush. The more you work the varnish the faster the solvents evaporate. If you see bubbles after the initial brush strokes leave them! They will work themselves out and pop before skinning over. Depending on the temperature your working in, thinner is typically NOT needed, but if it's hot or if there is a breeze then add 10% mineral spirits to help with flow time.
For laying the epoxy either roll it on and tip it off with a disposable brush or just brush it on with a cheap brush; it flows out pretty well on it's own. Pull as many of the loose bristles out as you can. Also, trimming the length of the bristles to about 1 inch helps as well.
** One important note on the epoxy is that it HAS to be a clear. This is generally determined by the hardener that is used.
Check out the link in my signature below. I have a 2 part video on this very topic. Should give all the info you need to make a decision.
Nope....just ext. plywood....basic tinny rebuild....but my dash is solid mahagony, was gonna use marine spar varnish on that and a combo of epoxy and spar varnish for the plywood (epoxy base coat with 4 coats spar varnish over it)
Re: What is the best way to apply varnish to wood?
You'll get a much better finish on the mahogany dash if you use the epoxy there as well. Mahogany is very grainy and using epoxy first will fill the grains in 1 or 2 coats. If you use straight varnish you'll be looking at 5+ coats before the grains are even filled (then you'll have to start building up the finish so it lasts .) For adequate protection you'll probably be looking at 8+ coats if you use straight varnish. 2 coats epoxy, 2-3 coats varnish and you'll have as much depth in the finish as 10+ coats of straight varnish and a better level of protection.
.) For adequate protection you'll probably be looking at 8+ coats if you use straight varnish. 2 coats epoxy, 2-3 coats varnish and you'll have as much depth in the finish as 10+ coats of straight varnish and a better level of protection. 
