My purple sweater was a K3 P1 rib and I had to increase in ribbing too...
Here's what I would do for K2, P2:
Let's say you have 6sts:
Row 1 (inc row) -
Inc in first st by knitting in the front and back of the first sts. K the second st, p2, k1, inc by K1 in front&back of loop of last sts. (8sts)
Row 2 - (no incs)
P1, K2, P2, K2, P1
Row 3 (inc row) -
P1 in front&back of first st, K2, P2, K2, P1 in front&back of last st (10 sts).
Row 4 (no incs) -
K2, P2, K2, P2, K2
So you're basically determining your ribbing pattern from the center of the work outward instead of always starting your rows with K2 or P2, so your first st of every row is going to change. Sometimes the first st of a row might be P1 (or K1), but then the K2, P2 pattern continues across the row.
It's hard to explain, but easy to show. But I hope I did okay explaining :??