Sorry I didn't fully explain...when the engine gets a load of oil from the IC, removal of the glow plugs and use of a Shop Vac to drain the piston bowls of oil is as follows:
Get some small vacuum hose, smaller than the diameter of the GPs. Cut 4 lengths about 2 feet long. Run these to a length of PVC pipe which will fit the vacuum cleaner's nozzle. Drill holes in the PVC for all 4 hoses and then cap the open end of the PVC pipe. Now with the vac running, all 4 cylinders can be vacuumed clean at the same time. Oil and junk will take a while to settle and each tube will have to be pushed until it reaches the piston bowl.
Use clear hose, it makes the oil removal progress visible.