Some things that help, sometimes :
1) Squirt as many as you can reach the day before with PB Blaster (or SiliKroil). Liquid Wrench and WD40 are a joke compared to how well PBB works.
2) Get some 'needle nose' vise grip pliers, and use them to clamp the cages onto the nuts.
3) Work the bolt back and forth to help loosen the corrosion and let it fall off. Usually, I've found it best to start by actually tightening it just until it moves the least bit, then loosening a bit. Lather, rinse, repeat as many times as necessary.
Note that PBB is flammable, so if you use heat after applying it, you may have a small fire. Just don't panic, and it will shortly go out on it's own due to lack of fuel.