First of all, I don't think I would use that duplicolor. It is likely synthetic enamel. If it only says a reducer needs to be mixed with the paint, then it is. An enamel hardener could be added to improve it, but then your better off just getting a urethane which is a better system to start with, and cost won't be all that much more. Enamels are outdated and inferior to todays urethane and polyurethane finishes most people are using. And a base/clear system will have benefits which has been discussed before, so won't go into it. Check for a long thread singlestage vs base clear for one, and opinions. Really, when you are doing a thorough job, and going down to metal and investing the time to do things right, like you seem to be doing, you don't want to cheap out on the paint. Spi makes good products and are reasonably priced. There are many good brands of paint, but normally best to stick to a name thats been making automotive paint for awhile. PPG, Dupont, Basf, sikkens, really there are tons of good brand paints out there as well as some smaller companys that make good products as well. But I don't think that duplicolor would be a good choice for what you want for that nova. They are owned by sherwin williams I believe, but as far as I know, there primary market is touchup, engine enamels and aerosols, not making paint most bodyshops would paint someones car with. Even a cheaper lines such as omni or nason I think would be better then the duplicolor.
And those guys gave you good advice on epoxy priming. If it has sat in baremetal for awhile, you will want to give it a thorough sanding again. As long as its sanded in the 80-180 range, that should be good for now. Depends on what primers and how much you are using as well as who you ask. If the metal is truely straight, then epoxy may be all thats required. But normally most people go over the epoxy with a urethane or polyester filler primer for more fill and blocksanding. Number of rounds of filler primer depends on how straight things are looking. At the least, blocking out the filler primer with 180 grit, spraying a few more coats of filler primer and final sanding for epoxy reduced as a sealer or for paint. You have some reading to do, and there is a lot of good information on a whole lot of topics in past threads and the knowledge base. To give a list of specific steps would be difficult because we aren't there to see exactly what you are looking at as well and take a lot of space and time, and some things might not be absolutely needed, but by spending the extra time and money doing them will have its benefits. But you do want to stick to using activated products. but protection, ventilation and spraying on a warm enough surface are even more important then with 1 part paint.