I think you have your answer on the butyl!
I've never bought ready-made gel coat paste, but I've had great success buying pre-waxed gelcoat from Jamestown Distributors (
https://www.jamestowndistributors.c...Name=Evercoat+One+Step+Finish+Premium+Gelcoat) and thickening it with colloidal silica (West 406, Cab-o-sil, whatever). One can of it will probably be more than enough to touch up all your boo boos. What you don't thicken can be sprayed with a $5 Preval sprayer, rolled on with a foam brush, etc.
You may want to try your hand at tinting it though. Your boat may look white, but there ain't
nothin' as white as untinted gel coat.
Oh, and gel coat doesn't stay fresh very long at all. Once you buy it, you have to use it all within a couple months. Keeping it in the fridge supposedly helps.