Closing a mitten gap

I am making mittens and someone suggested to cast on 4sts if a pattern says to cast on 2sts then on the next round K2tog twice. This is when you have to cast on extra stitches after putting the thumb gusset stitches on a holder. That way it will close the gap a little better. It works great!.

Now I have another question. After the hand part is done I am starting the thumb. I am to take the stitches from the stitch holder (that has the thumb stitches) and put them onto 2 needles. With a 3rd needle PU 2sts from CO sts on palm.

Should I pick up 4sts here and then on the next round K2tog twice? Or will that make it bulky at the thumb?

I hope you understand me. :??