But i bet one of the DIY ski or snowboard sites has it all figured out.
Probably just to use a solid colour so you can't see the bubbles
i've only looked at a few of the sites , most have u-tube vids.
clear film is pretty common.
some are adhesive-backed for application , post cure or as a repair.
some , similar to the 'duravision' come with masking anticipating the need for adhesive.
one example i saw for skiis, offered the following:
-coat back of topsheet with epoxy
-coat top layer of ski with epoxy
-place ski in press
-place top sheet on ski
-add layer of smooth rubber on top of topsheet to better distribute load from high pressure bladder and prevent 'print thru' of bladder material
-bladder is located on top of rubber sheet (in press)
-raise pressure in bladder to 30-60 psi
-extra resin squirts out
-assembly is left in press until cured
-trim flashing and hit the slopes
the example in the vid was a clear top coat that looked nice.
but who knows?