The best thing that I have found to cut egg crate is a modified laser pointer. All you must do is remove the three little batteries that come with it and replace it with 2000 batteries and then you are cutting not just egg crate but buses too. Watch out for the table under the egg crate because that will be cut as well and if you are unlucky so will your floor. Try removing some of the 2000 batteries to weaken the power of the laser if you find it to be cutting to hot.
I use a hacksaw where the blade protrudes frrom the end.
Place eggcrate to be cut just hanging over the edge of a table.
Side of eggcrate perpendicular to your cut will stabilize your blade.