Usually mom will do a bang up job without any help at all. In fact, the entire premise behind Mama Heating Pad is to replicate (not replace) Mama Broody as closely as possible. I use it exclusively and brood outdoors even in the balmy teens twenties we have in the springtime simply because I don't have a broody when I need one, and have to order fertile eggs anyway! <sigh> So you shouldn't even need to hook one up, but I would recommend you have something in standby in case she abandons them or something unfortunate happens.
As @chickygirl7 said, do watch the waterer with the chicks. My one and only broody hatched chick froze his feet at the waterer when he was tiny and our temps had gone from the upper 60s to low 70s all of October and then plunged to 17 below zero in less than 30 hours. Yikes! Ah, the joys of living in northwest Wyoming! Another thing to keep an eye is that sometimes there will be a brave (or stoopid) chick that seems to want to wander around all over the place, and then not be able to find his way back. So do check for strays regularly and scoot them back to her until they figure it out - usually only a few days.
Good luck! And thanks for the mention, @lutherpug !
