They use a standard needle, here there called 15x1 , 20/20 or 100 x. hit a wally or jo anns it will be any thing on display, don't even ask for a 15x1 they won't know what your talking about . the needle packet will be labeled jeans. I look for the ones with the biggest eye.
I will no longer use joie or wallys thread. I buy from quilt shops and get the ploy cones at $5 for 3000 yds, buy several cones at a time.. never have problems with tension or breaking thread.
just guessing have done maybe 10 denims in this last year. 4 of those just this last August. I wasn't power quilting , I just had a system setup and cheap jeans where falling in my face, hard to past up of that ..
you really don't need a super strong needle denim isn't as thick as most think it is. wash it, iron it cut then sew, ironing makes it much easier to work with. that compresses the fabric, makes it stiff so it will lay flatter.