N80,
Most folks I know just sharpen them on the cutter.
To get your deck higher in order to get underneath, tighten the top link a bit, and park with your front wheels down hill. To make this safe, take a 4x4 or 4x6 post, cut a kerf with a chainsaw about 4-5" deep that fits on one of the tail wheel bracket members. Cut the 4x4 just long enough to be tight, and kick it into place. Set your brakes, leave the tractor in 4WD and in 1st gear. Now you should be able to sit or kneel underneath in comfort and safety.
I use a $14 4-1/2" Harbor Freight disk grinder to sharpen my blades. I touch them up every time I mow, and this takes about 10 minutes. IF you keep them real sharp, you can reduce the cutter RPM a little, making them stay sharp a lot longer. The grass looks a lot better too!