If the bridle is not connected to the harness, then it should not be that difficult, just conform the harness to the reindeer and the rest as I said should not be that bad the IK chain use for Santas hands then adjust the bridle at the other end. Unless the bridle is wrapped around the reindeers face, unwhich use IK chain it to the raindeer. This porcess is slower to describe than it is to physicaly do. Little tricks like this get you by when all the other availabe remidies don't work.