I bought a used pre-B 75 a while back, with very bad scratches in the front of the frame and slide, deep into the metal. The polycoat looked like crap. (I might not have bothered, but the gun has absolutely the best DA and SA trigger I've ever experienced in a SA/DA gun.... I bought it, even though it was obviously in sad shape.)
I used Automotive Paint Remover (from a auto parts house) and the polycoat came off in great lumps.
I then used a soft wire wheel on a bench grinder to polish it up a bit, and reblued it myself -- cold blue -- using Brownells Ox-Pho Blus and a mix of some other cold blues I had setting around).
It turned out remarkably well, and the finish has remained VERY attractive, after a lot of use, except on the back of the grip, where it has dulled a bit. Here, I hope, is an image of the gun from the CZ Forum, where it was originally posted.
The more you polish it before applying the finish, the shinier and darker the finish will be.
There are a number of new products out. I have one I'm going to try next -- Novum Solutions. I haven't used it yet, but have heard from several who say its great.
The American Gunsmith newsletter also rated Ox-Pho blue as the best of the traditional cold blues and noted, as does Novum Solutions, that you should heat the metal before application for best effect. (A hair dryer will do it...)
Try this link for Novum Solutions.
http://www.novumsolutions.com/
Either one of these will give you a blued finish without a lot of cost, and if you find it doesn't hold up, you can get it commercially blued or refinished later.
If nothing else, removing the polycoat yourself will save you some money if you have it reblued commercially. That is pretty stout stuff...