To finish the thumbs:
Transfer the thumb stitches from the stitch holders onto 2 double pointed needles. Use a 3rd dpn to pick up 3 stitches in the saddle of the thumb. Knit around, in the stripe pattern until you are ready to decrease.
Needle 1: knit 2 together, knit across
Needle 2: knit to last 2 stitches, slip-slip-knit
Needle 3: knit 2 together

Work these decreases in every other row. If you like more rounded thumbs, cut the yarn and pull through the remaining stitches with a tapestry needle when there are 6 stitches remaining. If you like a more tapered, pointy thumb, wait until there are 3 or 4 stitches remaining.