Scotch the tires? Is that the same as chocking them? I always carry four wheel chocks in case of some sort of emergency.
If you can't maintain enough air pressure to release the spring brakes I would not want to drive the bus if you could release the spring brakes. Sorry I can't help with fixing the actual problem.
It seems they mean the same
to block (a wheel, log, etc.) with a wedge, block, etc. to prevent movement
Origin: earlier scatch < ? OFr escachier, to crush < es- (L ex) + VL *coacticare: see cache
such a block, wedge, etc. used to prevent rolling, slipping, etc.
1. A block or wedge placed under something else, such as a wheel, to keep it from moving.
2. Nautical A heavy fitting of metal or wood with two jaws curving inward, through which a rope or cable may be run.
tr.v. chocked, chock·ing, chocks
1. To fit with or secure by a chock: The plane's wheels were chocked and chained down.
2. Nautical To place (a boat) on chocks.
As close as possible: had to stand chock up against the railing.