I am installing 18" Cedar siding boards. My problem is installing them around a bay extension where the angles are 22 degrees. No matter how precise I cut those joints, they look awful. I waste more material than needed and I cannot make the joints look neat.

I have had to resort to using polyurethane glue to fill-in the gaps and then sand them for painting, but they do not look good and its difficult to recreate the groove look on the glue.

Any suggestions?

Did you try overlapping them so one edge is even with the face of the next?
What about using a table saw set at 11 degrees?