Stairway molding

Hello, I'm new to this forum and I'm hoping that I can get some help. A friend has asked me for help and I'm a little defeated. He wants to add some chair rail molding on the wall going down the stairway to his basement. He got the flat wall done okay but now he (we) are having a difficult time with the other side. The wall goes up to the upper landing where there's an outside corner which leads into the kitchen. This the problem I having, the molding angle coming upward is about 35* and the from the outside corner trim on that wall into the kitchen is a straight line. When I cut the 35* angle cut, the wood edge is wider than the trim is without the cut because of the angle.
So I can't figure this out. ThankS in advance for any help that can be offered.