DIY Concrete Countertops 4

I had my friend Jesse come by to assist Elisha and I with the concrete countertops for the bathroom (we should have got a 4th person for the large piece). We let them cure for around 4 days before taking off the mold yesterday. The small piece went relatively quick to unmold and set up on a sawhorse to sand. I was going to use a grinder so we tested its power on the back side and man is that dangerous. I am going to get some lower grit sandpaper for my palm sander now (to expose the glass and aggregate beneath concrete surface because the grinder works too quickly) before the concrete cures too long and is difficult to sand down. After unmolding the large piece it looks as if the concrete wasnt quite thin enough to work around the glass pieces - Ill have to experiment and see what can smooth it out better.