I use mnemonics to list all the steps for my Students with LD/short term memory issues. For example:
Can I subtract the ones?
Over to the tens, borrow one
Add it to the ones
Tens turn, subtract or bring down
COAST spells a real word for the kids and if you teach the strategy listing the letters and make the kids fill in the steps first, then have them try it with the math, it should provide enough repetition to make it stick