When we prep a blend panel I typically like to start prepping (after removing all necessary handles, moldings etc) with 800g on a DA sander. This will help cut any existing peel and minor imperfections. it is critical to be very careful on the edges. if you burn through the clear you will have to put color there! after the large areas of the panel have been sanded I prefer to use the 3m scuff paste wet with a grey scotch brite pad, rinsing regularly. Next I like to wash the vehicle and blow everything dry before going into the booth.