John,
Looks like you may have already cleaned your roadbed, but if not I used Dawn detergent on mine with the previously mentioned medium stiff bristle brush with good results.
Just to add to the R Johnson repro roadbed discussion, he also made it for the Kline/Lionel 54 inch curves. Sometimes you can find it on eBay.
As for glueing down the roadbed I used Alex DAP in a caulking tube and it works great, had to remove a few sections, and just used a 3" putty knife to cut/separate the roadbed from the plywood. This stuff sort of rubs off the road bed like rubber cement.
I attached a couple pictures.
Afllyer
