When you're blind on exit, see what you can do, what you can feel, and pay attention to what is coming to you. The mental body will develop at a certain rate and you cannot force it. Kurt once told me that there's basically no recipes for developing it "out there" (meaning books etc.) so people try to make do with astral body recipes, not even realising they're in the wrong context for them to work.

So, if you spot exit blindness, roll with it. If there's something to accomplish, it will become apparent. Take in what comes to you and work with that. If nothing much happens, try to move, try asking for help or inspiration, or simply feel that body. If there are guides or contact/touch, roll with that.

It's almost cosmic irony - ideas like "this should work like this", "I should be able to do that" and "It would be best if I do this" are all typical mental body constructs. They can prevent going with the flow of what is really happening. While you cannot force the process, you can help it along by paying attention to any hints, going with what the experience presents to you, and so on.

I wanted to make a timeline comparison how long it took myself to activate chakras 1-4 of the mental body. I haven't had blindness in an experience since the heart chakra seems to have become functional. But I must have recorded my dream journal till then in the old forums, and so it seems like I've lost access to it. All I can say it took quite some time.