I used a long thin rod that I fed down through the top well. Had to disconnect the fabric well to get to the opening. Took me several tries, but I was eventually able to get them in. You're right, they are a PITA...very tough to get the proper leverage.
68 400 convertible - recent purchase
Used to own: 69 400 convertible - Winward Blue 69 350 convertible - Verdoro Green 69 350 coupe - Matador Red
I did something similar. Took a blunt ended chopstick, put a dab of dish soap on the grommets and pushed them in by applying steady pressure. They are a pita...
I'm not sure what Gus is talking about( not sure I want to) but are you guys talking about the grommets in the mounting feet for the pump? If so, looks easy to get to from behind the back seat.