I've done the Buffalo to Albany ride on my own a couple of times. Simply because of the history of the canal, you're never more than 10 miles or so from the next town large enough to have at least a convenience store, or more often, a full blown grocery. Access to food is of no concern whatsoever.

For camping, you can always stay at the locks ( though some are in the middle of towns, so might be less pleasant because of noise, etc. ) and often at tended bridges. There are dedicated free camp areas at Holley, Middleport, Brockport, and Newark that offer bathrooms and showers. Holley is my favorite--it has a lovely park. As mentioned elsewhere, the western part is more rural, so you wouldn't have any issue finding a stealth spot, but once you get east of Rome you're hitting more urban areas, and mostly on-road riding, so you might want to check for paid campgrounds if you're in the mood for a shower.

The last couple of years there's been a ton of work done on the path--both in terms of extending the off-road sections, and rebuilding the existing ones. It really sucked in a bunch of places a few years ago, but is now is pretty good condition. I did Buffalo to Rochester last year and it was pretty much perfect.

It can however get a little tedious sometimes because it's often miles and miles of nothing but the canal to one side of you and trees to the other, so as mentioned, going on-road to bike route 5 may be a good idea.

All in all though, I love the ride; it's incredibly relaxing.