When I need to make angled cuts for molding I use this method:

Draw lines parallel to each wall that extend beyond each wall so the
lines meet. Make sure the lines are the same distance from each wall,
I just place a ruler against each wall.
Connect the intersection point of the lines to the corner of the wall
and that is half your angle.
Use your bevel gauge to 'read' the angle and set your saw.
Can't take credit or this, I saw/read it somewhere.

Never tried coping or crown molding but crown molding can be made easy
according to these guys.
http://www.allwoodwork.com/article/w..._made_easy.htm