Small update:
I started sanding down the first layer of ABS cement, and started to identify the first set of low spots.
The space where the clock used to be will take a few rounds of sand and fill. The rest will probably get two more rounds.
The above shot shows one of the low spots on the left side of the screen bezel. After the next round of fill and sand, it will almost disappear and the contour will be closer to the final shape.
Using the ABS cement is easy. I have these little plastic bottles that were made for cake decorating, with tiny tips so I can siphon the cement in to the bottle, then just squirt it right where I need it to be. A thin layer takes a few hours to harden, and a thick layer takes up to a few days to be fully hard. This is pretty much the same as using ABS sludge, but without the hassle of mixing it yourself. It bonds to the bezels and makes the two of them chemically one piece, so I won't run in to issues down the road.
To sand it, I'm just using a flat pink eraser (remember art class?) with a small strip of sandpaper wrapped around it. This allows me to get into the small edges of the bezel, but still keep everything nice and flat. It's like a scale version of a sanding block.
The next layer of cement is starting to dry right now. More pics as soon as I get some.