Buffing/wet sanding advice needed

If it's really from bird crap you may have a problem getting it out, typically it eats right into your paint leaving it sort of pitted. I would take it to your local Shine Factory type place and ask them for their opinion, they buff cars all day every day and will have a very good idea on this. If they say they can fix it you may just want to go that route if you don't have the tools and products. If you want to do it yourself, I use Norton Liquid Ice and think it's great, I've also heard great things about System One and you need a good rotary buffer, probably $80 for the buffing product and $100-$200 for a buffer. Be very careful around edges, you can burn through in a heartbeat. If your paint is old it will be very hard and sanding scratches may be hard to get out, so I would try buffing first and see where that gets you. If you have to sand don't get very aggressive with it for that reason, nothing coarser than 2000 grit on old paint in my opinion.

The rust problem is a pain, ideally you want to sand blast it, I have a mini spot blaster that you put over the metal and it can isolate a spot the size of your fingernail, barring that you can try to hand sand as best you can and maybe try a rust converter to neutrilize what you couldn't sand out of the pitts. Epoxy prime it and then paint it. Unfortunatley it will only look ok from 10 feet or further unless you really go all out and try to blend it properly which is best left for the pros.