Dry fit first to make sure it fits well. Then mix up Thickened epoxy with wood flour for the “tabs” and the surfaces of the bulkhead that touch the galley flat. I put the epoxy on the bulkhead tabs/edges without adding any to the galley flat. This way moving the galley flat into place will reduce the chance of smearing epoxy where you don’t want it. I agree that thickened epoxy doesn’t really brush on… it’s more like spreading a layer of frosting on a cake. Once the galley is in place clean up any drips or smears. You will later fillet between the galley flat and bulkhead on the bulkhead side.
also keep in mind that you want to be as neat and clean as possible. drips of epoxy on the galley side of the bulkhead cannot be cleaned up once the galley flat is in place.
Hope this helps.