Hello, in my countree most of Hard Bait manufacturer use nitro cellulose disolved in acetone.
We have expirience ,allso ,with epoxy,floor warnish,and so far everybody use nitro cellulose because its elastic even it's very cold or very hot time outside.(winter-sommer).
Other coat have not this and when is cold it is wery easy to broke lures coat when hit it on rock or something simmilar .
That is experience in ex Yugoslavia area.Best regards from Bosnia :-)
ps Sorry for my bad English.