One shop I talked to told me they sandblast the anodizing and parkerizing then if any remain, thats when they’ll Cerakote. Another shop told me they remove the finishes completely, then spray the Cerakote. Anyone here ever done Cerakote over anodize or parkerizing without using blasting?

It needs to be roughed up with blasting but not removed for the best results.

Unblasted over anodizing will not be sufficient.

Directly from Cerakote's training manual

Anodizing is no problem. It’s actually best to leave it because it strengthens the aluminum. It just needs to be surface etched. As the poster above said 40 PSI will suffice.

However, some anodizing is shit. If any flakes off at 40psi I usually bump the pressure to ensure anything loose comes off before I coat. Depending on the color I will be spraying, I may do a black Cerakote tack-coat as a base prior to spraying the requested color to ensure color uniformity on all the parts. Example: I did a Noveske set and the anodizing held on the upper and rail, but flaked off in multiple quarter sized areas on the lower. Since I was spraying a light color (slight appearance difference over raw and black ano) I coated the lower with black prior to spraying everything the light sand color.

Park honestly depends on the condition and age of the gun. Fresh Park on a newer gun is fine with normal Cleaning and etching. On an older gun, it tends to hold contaminants a little better. I usually degrease, gas out a few times, scrub with a toothbrush and dawn, dish soap, and gas out of final time before I’m confident with it And throw it in the blast cabinet.

If you’re looking to DIY:
Early on when I first started doing my personal guns (Before I had the proper equipment) a red scotchbrite pad to the anodizing was sufficient for my purposes. You just need to make sure you get every crevice and inside corner. I still have two ARs I did this way and sprayed cerakote with the prevail spray jars. They are no worse for wear today then they were 5 or 6 years ago.