Re: solo training
I haven't read any books that are specifically about misogi. I know Mitsugi Saotome touches on the subject some in "Aikido and the Harmony of Nature." I feel this is a must read for all Aikidoka; it's practically my Bible. John Stevens also touches on misogi in "The Secrets of Aikido." I know there is a segment in there about waterfall purification. On a more practical level, though, I think mowing the lawn, taking a bath, getting a haircut, fast-walking or jogging, or raking your Zen rock garden are all forms of misogi. When I'm finished playing my saxophone for the day and clean it at night, that feels like misogi. There are hundreds of other ways through which to purify your spirit. Maybe you could invent some of your own!
I think doing sankyo on yourself can help reinforce the proper and most effective grip. Doing nikkyo on yourself can remind you to bend your elbows and demonstrate precisely where the pain occurs. I don't know how in Sam's hill you can do ikkyo on yourself, but it would probably have benefits too.
I recommend doing a search on this site for keyword "misogi." You'll probably get a million results!