Youu could  just do some simple gridwork exercises. 

Like doingg, pole, then jump,  then pole,  then jump.  Or doingg some bounce jumps.

Hope this helps  (:

Stirrupless work will help yourself get a lower leg. Also identify what your main problems are

For example it could be that you don't release enough, a problem that I have! I think everytime I jump three, two, one RELEASE! and eventually you train your self to do it naturally like you do with everything else in riding :)