Should I use white charcoal or erasers?

I'm 14 and a pretty good artist, and I use charcoal. However, in my drawings, I'm never sure if I should use my white charcoal or an eraser for highlights because sometimes the white charcoal doesn't look right or looks slightly yellow. I don't have any money for art supplies, so I can't buy a really good eraser and have to work with what I already have. I have a kneaded eraser, but it doesn't work very well. In general, what should I use?