I used rubber lube, from a tire shop. Same thing they lube tire beads with for mounting on a wheel. It feels like soap & I'd bet hand soap would work fine, too. Grease tends to attack many types of rubber, so I wouldn't grease the bushings, as you said. Silicone spray? Maybe.
The MB bushings I got didn't have the fabric lining. Yours sound like an imrovement. Then again, mine were stock 260E businigs, not the super duper 500E goodies.
