I did the following which worked like a charm. Mine were extremely rusty.
- I bought 12 pipe caps - metal caps that screw on to the end of steel pipes used in plumbing.
- Filled each cap with PB Blaster Penetrating Catalyst.
- Jammed the caps up to each bolt using wood shims
- Left it over a two day period to work its way in
- Used the correct tool for the ones that are difficult to get too, cannot remember where I got it from. Either way, use good quality sockets, quick snap, not slow wrenching.
This worked for me, but each car is different, good luck