Quite some time ago I noted that if you want a nice glossy head on your thread two coats of cement are preferred. But my suggestion is to wait until the first coat is quite dry before you add the second. When I do wait, the second coat seems to really stay on top instead of wanting to also soak in. 
i use guderod, check the spelling, rod varnish, have used it for 5o years or so. they have changed the formula a bunch of times, but it still gives a nice high gloss finish with one coat
Almost two years ago I discovered the joy of UV cure resin. One of the things I hated previously was having loads of flies drying between coats. A recipe for disaster!
Now I can give them one coat and a quick zap with the laser and job done. I now have two different ones on the go. Diamond Fine to seal the head, and Diamond Hard to create glossy heads. The time it saves me is worth the expense alone.
Cheers,
C.
Sally Hansens Hard as Nails works for me. Someone had to suggest it first 
I use this, but dilute it 3 parts to 1 part Acetone. Note that I use straight acetone, not nail polish remover. The remover often has additives that precipitate out and form a milky white solution… anything but the clear head cement substitute desired in the first place. But by diluting it with acetone, I find it flows into the thread wraps better.
Personal preference - your results may vary.
-ZugbugPete
I also use SH diluted with acetone. I also like Griff’s thin for small flies, which you can’t get any longer. I did find two bottles in Parks Fly Shop and bought them