There isn't really a "perfect" program for editing fakes. Whatever program works best for an individual should be the one they use.
Some options to look at:
Paint - everyone with Windows has Paint, and it's quite easy to use. For that reason, I would guess that most fakers use/have used Paint to create some fakes. It takes some practice to get really good with it, but you can make some excellent fakes with Paint if you know what you're doing.
Paint.NET - it's like MS Paint, only better. There's a lot more features on it, including layers, which can be a huge help with faking once you've mastered them. Special effects can also be handy. It's free too.
PhotoShop - a very professional image editing program. There's a ton of features and options which can be a real help with editing fakes. The biggest downside, however, is the money it costs to purchase this program, and the time it takes to learn.
GIMP - like PhotoShop, but OpenSource. A great program, and there's lots of tutorials online which can help you learn how to use it.
All of them can do the things you mentioned in your first post.