I use software called Edius. It is user friendly software. I cannot do "picture in picture", but I can overlay images, what also is fun to do.

An example is this video (vocals done by a friend of mine, and all guitars by me, recorded over a backing track) :

https://www.youtube.com/watch?v=gkYR_JDs7pI

or also this one (lead guitar by me) :

https://www.youtube.com/watch?v=5V7KRlIbPoI