I’ve been using Export to Shake, and AE for a long time… But you’ve got to be good about naming clips and keeping track of them going into/out of FCP. You can usually just Export-> QT Movie (with self-contained turned off). Open that straight in AE and off you go.
Just recently got Silhouette roto & paint…. LIFESAVER. For those quick rotos and paint-outs it’s such a huge timesaver. It’s got great rotomask features, and a pretty good paint module.
The 8 point mask in FCP is absolute junk IMHO.