Try watching Kelley's Mitten Class on youtube. You can just cast on for the cuff, work as long as you want and bind off, basically. https://www.youtube.com/watch?v=i2CZ_bMzk_k
As long as you have a pretty good idea of your gauge and how large you want the mittens, you really don't need a pattern IMHO. She shows gusset and afterthought thumbs. There is also a mitten video for purchase on this site that is more of a guide to follow than a pattern as I understand.