Get yourself a good folding protractor to measure each corner, inside or outside. This will save a lot of time and scrap. If you want to go to the extreme of coping a profile duplicator will be of help as well.
I learned here it is helpful to precut and mark several inside and outside angle samples from scrap and pair them up as you work.
Also borrowed a power nailer with great fast results. Will NEVER use the hammer again on molding. Leaves only tiny holes, almost no touch up ....WOW loved it so much I bought my own for future.:thumbsup: