First, make sure that you continue pointing RedSn0w at the iOS 6 beta 3 IPSW. It’s possible we could see a new version of RedSn0w released in the future with full beta 4 support, but for now, just redirect it.
Also, keep in mind that just like the iOS 6 betas, the version of RedSn0w used to jailbreak it is for developers only. It’s mostly for jailbreak devs who want to update their Cydia packages to support iOS 6, and it doesn’t even install Cydia on your Home screen.
If you are going to jailbreak, you can find RedSn0w 0.9.13 dev 3 on our Downloads page. Our beta 3 jailbreak tutorial should still work, but I imagine Jeff will be along shortly with a specific guide for beta 4. So stay tuned.