I'm new to oil painting - and I just finished a piece that had a lot of wet on wet blending. I managed the blending without problems EXCEPT at the end of a stroke it would leave a brush mark. So the blend was free of marks until I lifted the brush off, and then it would leave a mark. Ive tried everything I could think of - different brushes, less pressure. I ended up going back with my pinky and ever so gently trying to blend them out - which half the time created a bigger smudge.