for noseblunts on ledges, your best bet is to start off with a ledge that isn't too tall, and has a beginning and end, and isn't too terribly long, maybe 5-6 ft, and wide enough to ride on.
What I found that helps is to do a couple nose manny's and nosegrinds to sorta brush up on the ollie-into-nose-trick feel, and then when you feel comfortable, ollie like you're gonna nosemanny real close to the edge and just turn it a little and poke your front end down enough so that it locks in. I say to approach it like a nosemanny, cause that way even if you don't get into it that great, you won't slip out akwardly onto your hip like when trying noseblunts in the middle of a ledge goes sour. The sick thing about noseblunts fs and bs is that you can be sorta light-footed with it and just sorta dance around it till getting into it starts feeling good. So just start off sorta slow, ollie big, and put a lot of effort into getting your nose locked in on the edge, when you've got that, start going faster and forcing it like you would a lipslide, pushing it and making it slide is all in your front foot, your back foot more or less will just help turning out of it. I prefer going back to regular, it feels sicker. So when you're sliding it good, keep your shoulders wound back like when you do a lipslide or tailslide to regular (check Heath's tailslide posture for an example). When you get to the end of the ledge, just use your shoulder momentum to forse that pig off the end.
Once you got that shit dialed, you can start trying it in the middle of ledges and on hubbas n' shit, it's definately a cool feeling trick down stuff. Plus once you've done a few, you've got it forever.
There's one at 3:13 I did if it helps to see one at all, or validates my step-by-step
good luck, and report back with your results