Open a image in ps, duplicate the background layer, de-select layer visibility for the bg layer or fill it with a color so you can tell how much has been erased, etc., zoom in a little if you want and just use the Eraser and/or the Lasso tool. There's probably other ways of doing it but thats how I cut my shit out. Sometimes different methods need to be used. I'm still learning though. Fuck around with it and find whatever you like best.
my .02c's