Default [Q] How to downgrade to gingerbread from v28b pre-rooted?

I need help to downgrade coz if I flash directly to 2.3, I will get a bootloop... I was from XBSA V7 rom and I flashed to 2.3, didn't work so had to flash to pre-rooted v28B official leak rom. I can start the phone and all, but I really need to change back to 2.3 as I need to trade in the phone...