I got the disc sander going again and 60 Grit the coasters and timbermate.
I then switched back to the half sheet sander for 80 120 and 240 grit.
I found the easier to control everything by using the cork backing gripping the concrete driveway. Blew the off with compressed air between trips to the bin as I swapped out various grits. Mind you i didn't see a real difference, (apart from my stocks of sandpaper reducing!) but the surface was getting slippery to touch so I called it quits at 240.
Applied a first coat of surface finish and packed up for the day. Not a lot of progress in this post as I was plagued with intermittent rain all day.
So as a form of compensation I will do a "Beal Buff "on one just to see the effect, and satisfy my own curiosity as well.