The only other thing I can think of to try is to open the shocks and make sure there is a layer of grease between the springs and the housing, and then while the shocks are detached, see if the swingarm itself is what’s squeaking. I’ve never had the pivot point apart on our cruiser, but it’s possible that the squeak is coming from the pivot point.
I’m a big fan of CRC lithium spray grease, for problems like this because it can sometimes penetrate deep enough without taking things apart, but dries into a pretty durable film of grease. For the internals of the shocks I’d use conventional wheel bearing or silicone grease. Whatever you have access to should be fine.
I guess another place for squeaks could be the pivot points for the shocks themselves. They have to rotate a little when the rear swing arm moves, so they can use a little grease as well.
-Paul from ESG