Did you say that I can use Rustoleum as a top coat for my White bedliner?
You can add some powder to the tack coat. It is just generally recommended to be somewhat more liquid than the general coating application.
If you are referring to the oil based enamel, Rustoleum or similar can be used with our clear products as a color tint, but not recommended for a top coat. It is too soft, too slow in drying, not durable enough, and does not adhere very well. All those things except the slow dry can be compensated for when adding to our clear, but it is not durable enough for a coating.
If you are referring to a spray can product, you “might” be OK with Rustoleum, but we would very highly recommend automotive paint applied with an HLVP or similar sprayer. It would not be terribly expensive, and would be a more professional job. That, or out Ultrathane White polyurethane was what I recommended as a top coat to keep the White color. You could probably get a quality polyurethane from your local paint store less expensive than auto paint. Just be sure it is not a water based product as that does not adhere as well or last very well.
Again… Just be sure that you wash off or wipe down with mild solvent, and oily surface (if present from amine blush as mentioned). If much over 24hrs, you may want to consider a light scuffing (only if you notice a glossy surface)… it depends on texture you applied.