For an inside corner I'd put one piece flush to the wall, then bring in the
second piece and trim to fit next to it. You can scribe a line and then cut
it with a jig saw of use a plane or rasp to get a perfect fit.
Outside corners are tougher. You can do a lap joint and plane to fid, or you
can use a corner trim that may or may not stain the same color if that is
the finish. Many years ago, my step father used to do mitered corners on a
job like that and in 1970's dollars, he'd charge $25 a corner to do it. He
had the skill for that to make it look like a solid piece of wood.
Yea, the best is mitered, but even with the best of tools and reasonable
straight walls, it is a bear.
--
Joseph Meehan
26 + 6 = 1 It's Irish Math
Easiest way I've found is to make the corner section in the shop and
then field-fit rather than try to fit the miter itself onsite....