When attaching Han's pieces, and blending in to the base, you might want to try Latex caulk. Once you run a pass over the area your working on, you can wet it with a spray bottle and work it out very smooth with a smooth foam sponge to blend in edges. If needed you can make a couple of passes to get a really smooth seamless blend of edges or surfaces this way and eliminate a lot of the drudgery of endless sanding !!!