First few steps went ok (downgrade, prefs://1f) but the wifi just couldn't turn on. Whatever I tried the wifi didn't change from disabled/grayed.
Actually I just need to activate the phone somehow because I can program turbosim by the first phone. But no luck, I just cannot find a guide how to activate iPhone at least.
So for now, I have one fully functional iPhone and an iBrick (not really a full brick but the same functionality wise).
I was having some problems installing applications via installer.app (crashed when trying to install anything) but I found a great guide what to do:
ssh to your iPhone and then enter this:
cp -pr Applications /var/root
mv Applications Applications.old
ln -s private/var/root/Applications /Applications
rm -rf Applications.old
This worked great.
The original info can be found on this board.