Well, throwing yourself into Falco doesn't actually stop him from moving, so uhhhh...I don't know about that. I wish it did work because I'd love to be able to just jump out and take 7% from a side-B to guarantee a kill rather than having to cover it properly lol.
Basically just watch good Marths (Mew2King in particular) and copy what they do; that's the answer to most qustions to be honest. A lot of edgeguarding is about recognising the situation effectively so you know what options you have to cover (and then being prepared to cover those options: knowing what you have to do, what position to be in, etc.). You can start with simply knowing when they're far away enough that they can only recover to ledge and not on stage, and grabbing ledge to cover that; that's free. Generally if they can side-B or jump you want to get ready to cover that first since it's fastest, then you can react to up-B or shine stall and cover that afterwards. Practice executing grabbing ledge, and refreshing your intangibility on ledge (by regrabbing it).