Some bushes are bonded, some aren't. Each has its own advantages, and in our case we almost always use bonded bushes.
I don't know how to get a good bond, I know this can be problematic. I'd guess the surface finish and cleanliness of the metal is paramount, and the correct primer is essential. If the bond fails at the edge of bush that is usually due to poor design - the fillet has to be carefully designed to minise the stresses in the transition.
Cheers
Greg Locock