Obviously not fixing the root problem... and all this 'cleaning the plate' - do you mean centre plate/ friction plate?
You cannot clean that, as said above, once oil impregnated, you're just cleaning the surface unless you soak it in something like hot Carbon Tet or MEK, pretty lethal to be around. Otherwise the minute it gets hot and pressure comes on, oil squeezes out again. And has this a new pressure plate (cllutch cover), or has this been severely overheated too?
Do both gbox seal and crank seal and spigot bearing, checking the spigot itself for surface finish and tolerance. Check rock of spigot shaft coming out of gearbox - it will move of course, but does it seem excessive?
If the flywheel boss that the seal runs against is heavily grooved, get it turned down or ground down to at least a smooth finish, though don't go too far. If the flywheel face is blued, cracked or wavy (a good engineers straight-edge will tell you, even a couple of thou), it will need grinding to some extent to true and de-glaze it (can't be turned accurately due to hardness), the cracks if small are Ok in themsleves, or get a good flywheel (check that seal boss though).
New centre-plate, assemble as:-
Clutch re-installing
might read this about looking after your gearbox:-
Reluctant gearchange
...and finally, ensure the clutch system is not holding the clutch open (hydraulic lock;
seized operating arm pivot bushes!)