Every surface that the epoxy is asked to bond with has to be clean, abraided, and able to accept enough material to make a bond - but not so much as to "sag out" or exit the bonding area.

If the surface is not abraided, the epoxy simply peels away and does not bond. Mix your epoxy on a piece of flexible smooth plastic and peel away an epoxy "cookie" when you are finished. It won't stick. Take that same plastic and rough it up and the epoxy will bond to the little gaps and scrapes in the plastic. The shim or ferrule is smooth plastic as you get it from the factory - you need to rough it up.

The use of shafting beads to help fill a small void is acceptable and will actually strengthen a bond if used in the right amounts - however if you try to fill to large a space, you'll "sag out" and pull away from the walls, weakening the bond. If you use too much bead material, it will interfere with the epoxy's ability for parts A and B to react correctly and cause a weak bond.

Any shim, of any material type, needs to be cleaned and abraided. Metal or plastic, it makes no difference. The best bond comes from a clean and abraided shaft, using a clean and abraided shim going into a cleaned and abraided hosel.

Without this cleaning and abraiding you may get a bond, but you will get a better bond if you clean and abraid.

The inside of a ferrule needs to be abraided if you don't want it to eventually walk up the shaft. The shaft under the ferrule needs to be abraided (at least part of it) in order to hold securely as well. to the ferrule. Skip either of these steps and the epoxy stands no chance of holding the ferrule in place for the life of the club.