With most of the veneer and wood glue scrapped off the wood trim, you can start hand sanding with a course grit to removed any remaining bits on the surface. Take care when sanding around the edges, they need to remain sharp and even.
With that complete, we would suggest sanding the wood trim either by hand or electric sander with a finer grade paper. This will remove the smallest of imperfections to give the wood trim a smooth surface to apply the new veneer to.
