Acrylic Urethane is a single stage paint, meaning you add hardner and in some cases reducer, apply the paint and the paint dries with a shine...if it's applied right and there aren't any metallic's in the paint. If the Acrylic Urethane has metallic's in it, well you will be working the paint real hard to try and get a shine...it's the nature of the beast. It should also be noted that Acrylic Urethane's and Poly Urethane's do take a substantial amount of time to dry.
A Base Coat paint generally does not take a catalyst just reducer (some manufacturer's recommend small amounts of hardner, paint such as Dupont's Imron use a hardner, however that paint is most commonly used in fleets such as tractor trailers, are difficult to repair in many cases), dries rapidly, in most cases 15 to 20 minutes and a Clear Coat needs to be applied to give you gloss your looking for.
You do not need to re-tape between automotive Base Coat and the Clear Coat. It is a very good idea to use a tack rag between coats of Base Coat and very important to tack between your last coat of Base and your first coat of Clear....DO NOT TACK BETWEEN COATS OF CLEAR.
I hope this answers your questions