When it comes to card sleeves, I recommend Mayday Gamers' Standard 2 1/4" X 3 1/2" sleeves. They fit BANG cards like a charm, and should work for your custom cards if you trimmed and rounded them correctly. The sleeves come in a 100 pack, and cost $2.25 on the Mayday site. As always, check Google shopping for the sleeves. When I checked both Fair Play Games and CCG Armory were selling them for $1.50 per 100 pack. I got mine for around that price at the local comic book store, so you might want to check there yourself and see if you can avoid shipping costs for something as small as this.
Shuffling with card sleeves is a little irritating, but you'll get the hang of it. Check out this video, which makes it seem a little worse than it really is (at least for me):
If anyone else knows of any better card sleeve options, feel free to post a comment here.