Roy,
You actually can get a squawk code for VFR flight following on the
ground sometimes. I have done it at BLM enroute to FRG. Called Bradley
on the ground and told them I was departing BLM to the north and wanted
to transition the Bravo....could they give me a code and pass me
thru..The Bradley controller took the info..called me back with radar
contact after I was airborne and then passed me thru the NY Bravo to
FRG no problems. I don't know if they will always do it..but what's the
harm in asking.