Use Palmettos stuff. It is cheap and easy to use. You basically add some to water and boil it in a stainless pot on a gas grill...Or in the house if you can get away with it. Pour clean bolts in and stir them like soup. In about 10 minutes you have phosphated bolts. Works great.
Palmetto Enterprises - Grey Phosphate Plating
2311 A Old Parker Road
Greenville, SC 29609
PH (864) 246 3836 He keeps threatening to retire...Nice guy