Rifle coating can be done by the hobbyist. It is not difficult to do. It does, however, require some extra tools/equipment. What, exactly, is required varies with the type of finish one plans to apply.
If you are only planning to do one rifle, it is probably more cost effective to have a smith do it.
If you plan to do more than one rifle or if you are simply interested in tinkering, then it might be worth it to gather the tools and equipment for metal finishing/coating.
I have experience with Duracoat and Brownells Gunkote.
Duracoat is pretty simple to apply. All you really need is media blasting equipment and an airbrush.
If you use Gunkote, you will need a curing oven in addition to media blasting equipment. Gunkote is available in a spray can or in a bottle, so it can be used with or without an airbrush. With a little bit of ingenuity, it is possible to build your own curing oven on the cheap.
It is my understanding that the durability of both Duracoat and Gunkote is at its best when applied over a parkerized finish. So far, I have only applied these finishes to bare metal and I am satisfied with the results. I am, however, preparing to experiment with Gunkote applied over parkerization.
Between Duracoat and Gunkote, I like Gunkote better. I strongly suspect that I will like Gunkote applied over park even more.