The two ways of dealing with wheelslip is of course to close the regulator. If the loco has primed, ie the water in the boiler has sloshed up into the dome after a heavy/jerky start, then it may not be able to close the regulator, if this is the case, as it was with the Blue Peter incident, then the valve gear should be closed to maximum cut off so very little steam is getting into the cylinders. and open the steam cocks to release the pressure. This has to be done very quickly once the wheelslip is out of control. The Driver of Blue Peter had his arm broken by the regulator handle flying back so was probably unable to do much else as the valve gear, connecting rods and cylinders self destructed and the axles turned on the driving wheels. The last line of defence is to drop the fire to stop any more damage to the boiler and locomotive.