Glad you got the bike running, Andy. Good job! I presume that it idles better now? If so, seems like the carb cleaning did some good.
You have the type of petcock with a sediment bowl, yes? If so, those can be had for around $50 on eBay, also
www.yamiya750e.com and
www.cmsnl.com carry them. You can probably find one cheaper if you hunt a bit, try posting in the Parts Wanted section here.
Sounds like your charging system is working at least somewhat, revving the bike for a bit lets you use the electric start, but don't expect the battery to charge up all that quickly. You need to ride the bike several miles at least to recharge the juice used up by using the electric start. Sounds to me like you just ran the battery down from all the work you were doing, once you're riding it you should be ok. If you don't already own a battery charger, now would be a good time to invest in a small trickle charger. Battery Tender brand is a good one. Don't buy a large one, a 2 amp charger should be good, charging at 10 amps or more will overheat your battery. Let it charge overnight.
As far as paint is concerned, if you're just looking for something to get you by than just use any old spraypaint. No spraypaint will be especially resistant to gas but some are better than others. There's a clearcoat called Spraymax on the market which is very durable, so if you want you can topcoat with that for enhanced resistance to gas. IF you're going to have it professionally painted though, I'd just spraybomb it with whatever floats your boat. A professional job will cost you upwards of $100 minimum, as the paint itself is more expensive and it takes special equipment and knowhow to apply. Forum member Hope had her
bodywork painted at the local prison for just the cost of paint. They also did a great job on her
seat.
Anyhow, glad to hear you're making progress.
mystic_1