Personally, I hardly ever use the crossfader. I feel I have more control without it. The best thing to do is know which frames match which. In addition to beat matching, you have to know where a track should be mixed in/out. Knowing every aspect of your music helps, along with practice.
Most of the time, when beatmatching, it is alot easier to bring in bass first, and usually leads to what in my opinon, less harsh transitions. However, this assumes the bass lines match well.
Remember, not EVERY track can be matched.