Yep, I'm a big fan of Judy's (JillysFullHouse) technique. Over 7-10 days, start pushing back your wake-up time by a half hour. After a period of time, she'll start making the connection that she gets up when your alarm goes off. If she's being crated at night, that makes things a lot easier. That way, you can ignore any whining without fear that she's going to have an accident in the house. I've even heard of people using a squirt bottle for the dogs that carry on for hours on end. If she's not being crated though, don't do the squirt bottle. That could cause her to stop giving you signals when she needs to go outside, which results in a dog that just slinks off and pees whenever she feels like it.
As for the bald butts, totally normal. Henry has a bald butt and minimal fur on his belly. We did a thyroid at one point (trying to diagnose his seizures) and it was well within the healthy range for a greyhound. Some people here recommend using 3g of melatonin a day to help with alopecia in greyhounds. It's pretty cost effective if you wanted to give it a try. I bought a 120 day supply at the grocery store for $5. Unfortunately, we've only been using it a week, so I can't comment on its effectiveness just yet. But yeah, if she's otherwise healthy, I wouldn't rush into any testing just yet. Who knows, maybe someday you can enter her in a "shiney hiney" contest.