When I do the technique, I put the oil onto a little cotton square (actually, a stack of cotton squares) and then touch the stump to the cotton.
Do you perhaps need to sand down ("sharpen") your stump to get rid of any color/residue on it? Sometimes, that gets a little smooth and matted and doesn't work as well. I sand it off on an emery board.
Are you working in small circles to blend?
Like Dini, it's been a while since I got out the pencils, but those are the only tips I can pull from memory (and from photobucket).