90 psi is gonna warp stuff pretty bad. i use starblast because it is very fine and will clean the pits out. leaves a good anchor pattern and it is very forgiving on warpage too. NEVER shoot 90 degrees at a panel or it's going to wave bye bye . blasting can be done with 40 psi with no problems. my rig runs at about 40 psi .
ps.......... playsand kills.