New to blender, need help with separating parts of model

Okay, so I’m trying to create a model for a video game character. I’ve already setup a bone structure and everything like that. I can move the character and all works well except for one part. When I move his legs, the pants “stick” together. Here’s a picture of what I have: I’ve tried fixing it with weight paint but it doesn’t seem to separate them. Any ideas how I can fix this?

With the automatic groups feature, sometimes vertex groups get assigned to both sides, so left leg weights are present on the right leg etc. What might be the best way to fix it is to delete all the groups on the pants and then start from scratch, otherwise you’ll have a heck of a time figuring out which vertex groups are still affecting the areas in question.