There are short videos and write-ups of techniques at this site.
This is a video on slopers.
“How do I use them? Watch the video. You’ll notice how Glenn really gets his weight as far under the hold as possible. The aim is to try to get as much friction as you can by placing your weight under the hold. The higher up your weight, the less friction you’ll have. This can make it difficult when you want to move upwards to the next hold as you can slip off as you move up. In this case try to keep your forearm as close to the wall as you can. Stay as low as you can until you have reached the next hold.”