Since the yarn I used was so large, I made the following changes:

Rib-edge Version
Wrist:
Cast on 14 stitches. I used sz. 13 needles and did not change sizes.
K1, P1 6 rows.
K plain, 5 rows.

Hand shaping:
Left mitt:
round 1: K to last 4 stitches. Next st, knit into st below. K remaining 4 stitches.
round 2: K all stitches.
Repeat these two rounds 3 more times (18 stitches).
K 14 stitches, place next 4 sts on a holder or waste yarn. Cast on 2 sts. Join and knit around (16 sts).

Right mitt:
Work as for left mitt to beginning of hand shaping.

round 1: K 4 sts. Knit in to st below 4th st. K remaining sts of the round.
round 2: K all stitches.
Repeat these two rounds 3 more times (18 stitches).
Next round, put first 4 sts on holder or wates yarn. Cast on 2 sts. Join and knit around (16 sts).

Fingers (both):
K plain, 4 rounds.
K1, P1 rib 6 rounds.
Bind off loosely next round in rib.

Thumb (both):
(What I did)….
Pick up 6 stitches evenly around thumb hole, beginning on one edge of the 4 waiting stitches and working your way around to the other end (3 stitches each on dpn).
Slide 4 waiting stitches to dpn.
Knit plain 4 rounds.
Bind off loosely.