The rock buckets do work well and they only push them tiill the tractor stops after the bucket is full. We sell ones that are made out of 1" round stock with points spaced about 2" apart to allow the dirt to fall out. It has a recessed area in the back of the bucket so the stones ou have picked don't come back out.
Have also been told they are great for lightly rooted vegitation.
The regular rotary rock pickers do work and are not normally used for clear picking as they tend to load up with dirt.
The hay buster units with this type of concentration would need to be run with a hydro or creeper tranmissioned tractor do to the volume.
A rock rake would windrow and make a regular bat style far more productive.
There are two types of rock rakes, landscape and ag, the landscape leave a fine top, the ag will bring them up from possibly five inchs down making the job more indepth.
A rock rake, rock bucket and a dump trailer would be awsome, maybe almost to fast.
Some companies will rent rock rakes, do you have a freind with a dump trailer?