Originally Posted by CJ7-Tim
Use 220 grit and sand the color coat until all the shine is gone. Pick a direction of sanding and be consistent. For example front to rear, or side to side. Don't sand in circles or criss/cross your sanding pattern on a single body panel. Sanding down to primer is not needed and would take you about 3 solid days of work.
Just curious, why not sand in a criss-cross pattern?
A random-orbital sander sands in circles, I use it everyday painting cars in my shop. I block sand in a criss-cross pattern to get straight panels on restorations. A sealer would be good advice also when painting over old paint. Keeps bleed-throughs to a minimum.
See some of my work here: Welcome to Speed and Performance
Not trying to be a smart aleck or anything. I just hate seeing bad information on the net.