I do them all the time. Once you do them following a good guide, they hare not at all hard. Not every set of instructions, however, says you MUST press and starch or size well before you start. You need to leave slightly more than the border width beyond the stopping point on each side.
My instructions from my wonderful teacher were to 1. sew to 1/4" from the edge on each side. 2. Fold the body of the quilt on the diagonal, so that one border is exactly over the other. 3. Use your 45* mark on your ruler to cut both borders at once, being sure to leave your seam allowance. 4. Pin carefully. 5. Sew from the inside out.
They do get tricky if you want to line up patterns of border prints, so do the basics on the first go.