I have just sprayed PPG base and DCU 2021 clear on my car. I have sanded the clear with 1200 sandpaper. I need to spray black hood and rear deck stripes over the clear then add 2 more coats of clear over everything. My question is do I need to use an adhesion promoter or is sanding with 1200 grit paper good enough?

You should have used and interclear. I've never done it like that myself, but I've seen it done before with no problems.