Re: solo training
I think misogi / stretching / meditation are healthy practices. If you have a jo or bokken, I recommend swinging them around some. I have a couple trees in my backyard. I pick out a spot and repeatedly try to thrust my jo right to that spot. Also, I do bokken yokomen "cuts" into the side of the trunk. If you know any jo or ken kata, they are perfect for solo practice.
You can always practice with a make-believe uke. Of course, this isn't as good as the real thing, but it's better than nothing. One of my favorite things to do is work on my tenkans (kaitens) and try to keep well-balanced. Walking around my house, I sometimes spontaneously do a roll on the carpet or a pretend irimi-nage.