-Build a drivers stand so it can be portable and more versatile. Place the drivers stand in an optimal area where the sun will not be shining in your eyes and the dust won't be blowing in your eyes.
-Till some clay in with the dirt so it packs better and the jumps stay together longer.
-A typical garden tractor/riding mower will work good to pack the flat sections of track by just driving over it obviously using the wheels to do the packing. You could even use it on the jumps if they're not too steep.
-If your building large jumps do it in lifts. Lay down 6" and pack, add 6 more inches and pack, repeat until you get to the desired height.
-Be sure the jumps are the entire width of the track.
If I think of anything else I will let you know.