For great pistol coating or service work, I'd suggest these well known firms;
Robar Guns;
www.RobarGuns.com Bearcoat;
www.Bearcoat.com Black-T;
www.Black-T.com or maybe Accurate Plating & Weaponry;
www.APWCogan.com .
The NIC-Cerakote coating from APWCogan.com is cool and the site has a link to a color chart where you can mix & match slide/frame colors on a duty size Glock pistol. Black, Brown, OD green, Tan, Grey, etc.
Bearcoat is impressive and the shop says it has a "lifetime" service policy.
Robar offers a lot & does a lot of military/DoD/industry work. I'd avoid the black Rogard coating. It nicks & scuffs quickly.
The NP3+ is very practical but is a dull grey-nickel based color.
Clyde