This article http://www.iphonehacks.com/2010/07/dev-team-apple-has-started-soft-shsh-blob-checks-with-ios-4.html states that Apple's new "soft" SHSH checks for ipod touch 2g(MB model) can be bypassed using redsn0w or pwnagetool allowing for a successful downgrade from iOS4 to 3.1.2 but how do use redsn0w to do that?