I have tried to apply joint topping as plaster on the drywall and my shoulder and legs are sore from just half way. There has to be a better way to apply this than by hand. A friend of mine says he just paints the drywall without plaster I don't think that's very smart...although it sounds easy to do than having to apply plaster.

So are you skimming the entire wall?

I think there is some confusion in the terminoligy you're using. Do you mean dry wall mud or plaster?
Tape on the joints and dry wall (drywall) mud goes on dry wall (drywall)
Plaster is different. Both are very physical if you're not used to it. If you're finishing dry wall with "mud" there isn't really an easy way.

P.S. If you are skimming as the other response mentioned, you can thin down the mud with water ( mixing it with an auger ) and rake it off with a wide mud knife or a spray painters shield. Some light sanding might be needed for the fine edges after it dries.