if car was painted once before.
how far down do you have to sandd down??
or what are the prep steps??
pleasee helpp...?
starting to do work on my hatch..

 

if you have a mil gauge, you can check (1 mil roughly the width of a hair). if your car is in good condition with minor bodywork i would block out the car with 400 then 600 (i prefer wet sanding ) without worrying about it.

but if you have a poor quality paint and many layers of it, i would strip the crap off. maaco paint jobs and so on.

oem paint jobs are around 5 mil's deep and i 've seen finishes about 15 mil's deep holding up fine (long story short).

a common problem with to much paint mass is "crows feet" or "checking"