That black groove is chemical so that confirms everyone is prepping the crap out of them, reason I ask is with 33's usually with 33's anytime it goes dry real dusty when it's hard then it's back off the prep get on a more cured 33 little harder and up on air some, just dry slick because of a light film of dust rolling across the surface then more prep little less air, the abrasion part is because if it's gritty it works the tire harder which builds heat quicker than No abrasiveness which requires less prep as well, bottom line there a lot more details to just saying dry slick. Your in the ball park at 5 & 4 if a lot of chemical is going down.
Good Luck !