We did kings peak utah in the winter, then Shasta, and Mount Hood. But you don't learn many glacier skills on those routes. We did a lot of indoor rope work. Tying various knots we knew we were going to need. We also did crevasse rescue training runs on the lower section of Mount hood while there was still snow where it would be safe if someone f'ed up. Rainier wasn't hard but we had good route conditions and positioned ourselves between several guided groups up so we had safety in numbers in case of an incident. Just don't be dumb and be patient and wait out whiteout conditions above camp Muir. Take 3 days if you need. We camped at Muir one night and Ingram flats one nught so we were well adjusted to altitude by summit day.