Tink, Hubby has lots of experience with this. He suggests that you take a section of the wall and practice on it using different techniques. It's best to have a semi-gloss or satin as your base coat. He asks if you are using a glazing compound?
One technique he suggests is to use a paint brush to create a vein effect and then lightly rubbing with a damp rag to feather it in. If you are trying to go for a leather look what you want to do is some veining, brush it with a damp brush to thin it out and then lightly rub with a damp rag.
The walls in this picture have a troweled on texture and were painted a yellow color and a chocolate glaze was applied by rubbing with a medium sized damp rag saturated with the glaze. The decorative painting was added a few days later.
http://i171.photobucket.com/albums/u...s/IM001545.jpg
The walls in this picture were painted a green and a slightly darker green was mixed with a glazing compound and the wall was lightly blotted with a small damp scrunched up cotton rag that was saturated with the paint/glazing compound mixture then squeezed until there was very little of the mixture in the rag.
http://i171.photobucket.com/albums/u...s/IM001522.jpg
Try different techniques until you get something you like and paint over the experiments and go for it.
There is no right or wrong, it's just trying to get an effect that you like.
Good luck, you can do this!! Let us know if you have any questions.