There was a period when the Alclad black was bad. Lots of people with the same complaint as you. Then the stories started getting better and it was chalked up to a bad batch a while ago. You may have gotten one of those. I use Model Master gloss back enamel and let it cure for about a week.
This brings up an important point. Unless you are using Alclad chrome or polished aluminum, you do not need the black under coat. As far as polishing, yes that is a good idea. Any minor scratch will stand out like a sore thumb from the Alclad.
Here is the technique I used that I got from a webinar given by master molder Floyd Werner. Sand all the seams etc. and get the model prepped as best you can. A primer coat of Mr. Surfacer 1200 is applied and allowed to cure. This is also a lacquer but goes down smooth and will protect the plastic from the hot Alclad. The Mr. S is polished with 6000 micromesh. Believe it or not, a clean coffee filter works pretty well too. Make sure you have a good clean surface then apply the Alclad.
Get a couple of really cheap models and just build the airframes to practice. It is way easier than all of what I just said sounds.