Need help with a butt ghost build.

Surveilance, Whispers, Pop Goes the Weasel, Whatever you want.

Surveilance will tell you when someone is on a gen after you kick it so you can sneak up behind them. You could replace this with discordance but if someone sees you and gets off the gen, everyone else is going to be looking to see if a killer is coming so they might spot you before you get the grab.

Whispers lets you know if you're near survivors who are probably on gens, but this means you can go into crouch to be quieter and walk standing to be faster when out of Whispers range.

Pop is your game slow down perk, this is better than Hex: Ruin in your case because with Ruin you might have multiple people off gens looking for it which means less people to grab.

Fourth perk should probably be a chase perk like Enduring or whatever you like.

Addons should be recovery speed and crouch speed, you don't need marking addons for grabs.