Metal looking ball dust in attic, dangerous

Not knowing where the house is limits the advice. However since it has a flat roof, I'm going to assume it's not anywhere where it snows a lot.

You need to get a professional for several reasons.

1. In most states, as a landlord, you're required to do something and the only way you can demonstrate due diligence with something like this is court is to hire a pro.
2. Animals carry lots and lots of nasty things, not just rabies (as if that isn't bad enough). If you trap it you risk injury, if you poison it then at some point you have to remove the carcass and ... gross.
3. The professional should be up on whatever obscure state and local laws affect removing the animal.

Most importantly, if the pro gets rabies, it's not your problem.

Edit: Yeah, I know it a Do-It-Yourself site, but sometimes the right advice is "Don't Do-It-Yourself"

Any reason you are not you are not using fiberglass batt insulation. This can be done your self with adding 2x4 on end to get at least 9.5 inches. Then staple the insulation up. no need for baffles if insulation is at least 1" less that rafter width. The cost saving will leave you enough money to pay someone to hang drywall on ceiling maybe even spackle.

Spray foam is a good product but expensive and your electrician will charge alot more if he has to run wires through it for lighting.