A solution I use on my BMW subframe bushings:

Two part liquid poly from McMaster Carr. It's about $30 a pint? and you can't store it, so have other stuff ready to fill. There's a primer you can buy to make it stick to the rubber, but I used the purple plumbers CPVC primer. It's available in different hardnesses- 94 is really hard and 80 is more like Energy Suspension hard (softer). I thought of using it on my mounts, but they seem to be fine. It would probably work good on the trailing arm bushings, if you can get it to stay put.