sanding down 2k primer filler properly mixed right ratio right thinners last i did this task no issues so buy some 120 grit wet and dry and 400 a4 type sheets ,,120 grit barely scratches surface. nip to toolstation for some aly oxide red stuff ,,and yellow stuff red stuff performs like rubbish so i try 120 grit yellow stuff which is better next i try white production paper 120 grit which performs really well -how i remembered it . i struggle to get more of the white production paper at min so use 80 grit yellow from tool station which is ridiculous fror primer filler ive tried 2 lots of primer filler cappi is one make and the primer filler is 534 off e bay mixed correctly 4to 1 .i am going to get my da out 125mm ,,,but which make disks to use =a lot of junk out there .