What you really need to do is get with a painter or paint supplier and see what black's are offered in the paint line of your choice. There are a few different shades of black's some black's will look almost yellow compared to some. Look for a black that has some blue shade to it. Glasurit has a #1250 deep black that is nice and rich looking.But all the paint companies have alot to chose from.If you have done your body prep and bodywork right there should be no reason to poly-prime twice and block four times.Find the right guy to work on your car and you should be able to poly prime and block twice and be where you need to be . Also don't waste your time sanding with #1000 on your first cut or it still will have some urethane wave when you look down the side of car. I think you can get away with it if you do a flow coat which has been 400/600 and recleared.Just my 2-cents Joe.
