After Apple released iOS 6 beta 4 for developers, MuscleNerd (the famous hacker & member in iPhone Dev Team) assured in his account on twitter that we can use the previous jailbreak RedSn0w 0.9.13dev3 for iOS 6 beta 4 .
JB devs can continue using redsn0w 0.9.13dev3 with todays iOS 6 beta4 (keep pointing redsn0w at iOS 6 beta3 IPSW) is.gd/MCbq7A
— MuscleNerd (@MuscleNerd) August 6, 2012
Download RedSn0w 0.9.13dev3 for Windows.
Download RedSn0w 0.9.13dev3 for MAC.
Watch the video to know how to jailbreak: