There are two things you can adjust on yor handbrake.
Firstly the shoes in the drums. Take the drums off, and there is a little, star shaped nut which can push the shoes further apart. Wind them out as far as possible until just before the shoes start dragging on the drum when you slide it on. It takes a bit of on and off with the drum to get it right. Also if the drum ahs a big lip on it, it'll give you the shits.
Then you should also pay some attention to the cable (adjuster is on the handbrake handle). Tighten it until the cable has lust the tiniest bit of slack in it. So as soon as you move the handle it tightens and starts to do its work. It's pretty easy to feel this point.
Then you're done. Go do skids.
Hen