While hydrodipping offers a variety of patterns and colors, most people that have done it seem to be disappointed by its lack of abrasion resistance.
I think dipping is an OK choice for stocks or plastic, but there are better choices for metal protection. And I do believe that you can final finish the product in gloss, or matte.
My first choice is Norrell's Moly Coat. I find it a good metal protection choice for a firearm. More of a phenolic based finish, it has great abrasion resistance, and pretty good chip resistance.
I am not a huge Cerakote fan (just a personal choice). While a fairly tough finish, it just doesn't hold up for me the way it has been advertised. (i personally believe that some of the issue is with the person that applied the finish. Make sure if you do go with Cerakote that the finisher is reputable and knows what they are doing). I like Duracoat also, one advantage is you can do it yourself, with pretty good results. If you leave it harden the 30 days, you should be GTG.
I have also heard great things about Birdsong T. As soon as my SBR project is done, we are going to give that a try.