I have looked pretty in-depth at dozens of coatins and surface treatments for baffles. The best ones are done by the PVD process, and there are very few companies who do it in the South East. Most of them are on the west coast. Any other film type coats won't survive the heat and abrasion.
For baffles to get done, they have to be an 07/02, or close enough and willing to let a responsible person come to their facility and babysit the parts while they get coated. I have found a shop willing to work with us, so that's something we are going to try in the future.
On the other hand, there's more to it than just stick on a coating. You have to look at the base material too. If the base metal is aluminum, it will still be pourous and soft. So stuff will still adhere and if you try too hard to clean it, you can gouge the material underneath the coating.
We use 6al4v titanium because it's naturally tough, and almost nothing chemically bonds to it. So if you ever want to clean your baffles like new, send them back to us and we will bead blast it to perfection.
I will say that the deposits on the baffles do help suppression, so long as it's not so much that it's reducing the volume significantly.