If you have a 4S currently SHSH blobs are useless for A5 and higher but in case a patch is found I'd try saving the SHSH blobs in iFaith anyway, just don't save check to save them from Cydia.
Go into Settings>General>Reset>Reset all Content and Settings
It's essentially a full restore without iTunes. Note that after you jailbreak if you ever want to go back you're stuck and the "erase all content" doesn't work any more.
If you still want to jailbreak, try redsn0w.