Prepaid cards, AFAIK, are very unlikely to work. So you are pretty much left with your Visa
cards or Western Union to deposit. Why don't you want to use your credit cards? As long as you keep an eye out for fraud (which you should be doing anyway, and will not be held liable for), you should be okay. (Although, I would only be willing to use a credit card, NOT a debit card, as the fraud reporting process can take time, and I would not want MY money tied up.) I've only deposited via UMW and Ewalletxpress (both gone now), so I can't give you much from my experience.
Only withdrawal methods right now from Carbon are checks / gift cards. You don't have a choice -- you request a check, and they send you one or the other. Cashout times seem to be getting faster as of late; my last withdrawal (gift card for ~ $500) took 2.5 weeks. They have / had been taking 6-8 weeks, though, and that was pretty recent.