Well, as you can see, there are a boat load of opinions on what works best for each of these guys.
A fast dryer, in the 36-45 RPM range will make getting a nice straight line and getting finish on all of the guides before your finish kicks much easier. It isn't necessarily the best for a smooth hyper flat finish however.
The speed you need for your dryer will depend a lot on the finish you use. FlexCoat, both the regular and lite, are fairly thick and need a slow dryer to level properly. These can be thinned, but why? There are low viscosity finishes available.
I have a 36 RPM dryer. 4 of them actually. I also have settled on ProKote from American Tackle as my finish of choice. ProKote is a low viscosity finish with a long pot life. It does take about 2 hours longer than FlexCoat to set for me, but I get a much better finish with my fast dryers as the FlexCoat does not have time to level as the rod spins. The ProKote will level at these speeds and looks great. I apply finish to all of the guides and the inscription area all at once on a rod up to 11 ft long meaning I don't have to mix multiple batches of finish which saves me money. I usually have time to go back and add a little finish to the stripper after the first has soaked into the tunnels alongside the guide feet.
You should not need to thin your finish. It is designed to be applied according to the directions which I have never seen to include thinning. The cheap nylon brushes should work fine for you if your finish isn't already trying to set on you.