I like the feel and warmth of thrum mittens but I don’t like the time spent making thrums. I found this Bernat felting yarn and used it. When I came to the spot to insert a thrum, I folded a loop of felting yan and placed it in the stitch.

Also since the top of the mitten and the thumb have less loops, I cut a long tail of yarn after the mitten/thumb was knit and used a crochet hook to create loops inside.