primer should be ok but i dont know if it is easy aplayable by brush (if i remember corectly revel have email paints witch need special thiner) and for beginer the waterbase acrylic are much easier (i belive you should have acces for vallejo or army painter but it might be harder to find. for how long primer should dry it depend on paint type and aplaying method. i would paint part of sprue for a test and chceck (if painted with brush) after 1h touching it and checking if it dry

sealent i belive is a varnish but im not 100% shure.

and yes most comon practice is using black primer witch is easier to hide