Rent a Skidsteer with a mulcher head.If you bulldoze into piles you still have to deal with the piles pulse you will loose top soil.I started with a bull dozer ,big mistake.
I would recommend contacting NRCS. We cleared about 160 acres in southeast KS. using the government programs. Can't remember if we used the "whip" or "equip" programs. Both are cost sharing programs. I would think the methods you want to use will depend on what your plans are. Also 1 of the drawbacks to the government program is; government rules apply. If it is going to return to pasture, then clearing the trees/brush can be done with tree shears, saws and bushhog. If the ag portion is going to return to production I would suggest a dozer to get the stumps. Our local office did not recommend a dozer for grasland clearing. Their recommendation was to save as much of the native grasses as possible. The cost of the native grass seed is very expensive. As stated in another entry this will be an ongoing effort to control the regrowth even if stump spray/killer is used. The upside is it takes less spray to kill sprouts as when compared to larger trees. I used a skid steer mounted saw for clearing and just piled the brush/trees with my skid steer for later burning. Brush piles also make some good habitat if piled correctly. I had some plans to do pasture clearing, otherwise it might be cost effective to have the pastures cleared with a contractor.