I posted this in GD, but it probably makes more sense here.

So there I was at the gun show looking at a vendor's wares, including some cerakoting. I've been thinking about having a single color "spatter" finish done on one of my fun projects (no Zombie) over the factory finish. Now I understand that some amount of surface prep is necessary, but the guy tells me the anodizing has to be stripped, and refinished for the Cerakote to "stick."

The cost? How about $350 for some Cerakote "Crimson" spattered on a stripped upper/lower/Troy Alpha.  

I'd already planned to use someone here for my Cerakoting, but I was wondering about his claims about getting the Cerakote to stick.

How much prep is necessary before you can get to painting?

Per Cerakote:

http://www.cerakoteguncoatings.com/resources/files/P-109%20Application%20Guide%20-C-110.pdf

1) Remove all coatings,  oils,  and  contaminants  from
substrate  with  either a de-greasing chemical and/or by
heating substrate to temperatures high enough to
remove coatings or contaminants.  

2)  A  lightly blasted  profile  (~40  psi) must  be  applied  to
the substrate   to   remove   any   rust,   scale,   or   other
coatings.  This is also required to ensure maximum adhesion.  
For best results use a dry grit material such as  aluminum  oxide  
or garnet equivalent to a 100 - 120 mesh size.  
Glass beads are not recommended as they are not aggressive
enough to produce a sufficient blast
profile.

Depending on how thick the anodizing is, the prep alone will either blast off the anodizing or at best it will cut through it in places.

So he wasn't shining me on then about it needing a base coat before the "spatter" could be applied. I usually have a healthy dose of skepticism for what I hear at gunshows. Thanks for clearing that up.

No problem, I thought it was pretty extreme when I was first told that, but I have seen what happens if you skimp on prep.  If don't give the Cerokote something to hold on to you can just scrape it off with a fingernail or it chips.

It would need to be blasted and that would make the anodizing look like crap.  It wouldn't necessarily need to be completely removed, but the etching would definitely ruin the anodized finish from a looks standpoint.

but for what you want it would work just fine not blasting it.

You can light blast with 40psi with 120gr Al2O3 and it isn't going to remove too much of the anodizing. If the metal was polished before anodizing to get a shiny look, it should be blasted more to a matte finish.... that will most likely remove the anodized layer.

You need to degrease well before blasting, then light blast to etch up the surface. My last lower I blasted before anodizing and didn't dye or hot water seal to provide a rougher surface. I used Gunkote instead of Cerakote, but the surface prep is the same. If someone else is doing the cerakote I would let them do what they have found to work for them, looks good and they will guarantee to stick.

I've had to blast off finishes from bad prep work and learned my lesson the hard way.