you could just lower the temp.....I've done that before......
it's a little tricky, you have to make sure the readings you're getting are right....if the 225 you were getting was higher, then a 180f reading might still be moving the cooking along too fast....make sense how I'm describing it?
I've, for instance, hot held brisket, on kettle, with a single row of coals burning to keep the temp @ 165 approx. for a couple hours........just warm enough, not really heavily cooking......
semi-loose foil, in a dry ice chest, NOT packed with towels (to allow a rest, without tight pack steaming) is another way.....then maybe a very short heatup near feed bag time...........