When using clear spray to balance props, what spray is used so it is fuel proof from nitro fuels ?

G'day Mate,
Use Clear Acrylic, comes in a spray can. Just use very light coats.

works great have used on glow or diesel no issues and quick light coats let it dry the solvent has a little wt till it drys off martin

Krylon "Crystal Clear" works well...
If you get the satin finish, it will make it just about impossable to tell which blade was sprayed after you're done. (I'm thinking APC here...other props you might want a glossy finish?)

It also helps, from a durability standpoint, if you scuff the blade to be sprayed first with very fine (600 or finer ) sandpaper.
(I wipe the prop first with denatured alcohol or wash in warm/soapy water to be sure there isn't any mold release on it...)

Are these Glow fuel proof????????????????????

Somewhat...just don't spill a lot of raw fuel on the prop and it'll work fine...
I have props several years old, and the main problem is it wears off the tips. (from "mowing" the grass )

Or you can use Minwax PU, spray the light tip, or just dip the light tip in a can of PU and let dry-only downside is it takes longer to dry but its fuelproof. Prep the same as stated above. If you want colors, use the old timey Rustoleum enamel paint.

Try a smear of CA on the light blade. No spray. No mess. (Maybe a stiff finger tip!)