I want to mention few methods that I use for rebidding:
1. I use Visa gift card with a $10 bal.ance
when Price.line asks for my credit card num.ber, I enter a Visa gift card with a $10 bal.ance in it, so if Priceline accept a bid that I don't want I can still have more chances to rebid.
2. Another useful method in some cities is using the rebidding tool at http://www.ibidlow.com that producing automatically the options:
A
AB
ABC
ABCD
ABCDE
3. Another thing that I started doing recently is rebidding again through my smartphone I now always have another IP address for rebidding

Good Luck to you all!