I love using multi coloured scraps from the quilt too, it's a great effect, especially if there are a lot of colours involved.
I use 2 1/2 inch strips, when you join pieces make sure they're joine on a 45 degree angle (so put the ends at right angles instead of together and sew a 45 degree line).
And for attaching it to the quilt, I machine the front, and hand stitch the back. Once you get going on the hand stitching it doesn't take too long.
:-)