i was told in a separate post that eggshell crate actually doesn't work well at all. now I'm confused.
eggshell crate and eggcrate foam probably work well for something, neither is much help in acoustically treating a room for recording.
everyone involved with recording has opinions concerning what works, by necessity most of the approaches used in home recording treatment are bad compromises between what you can do (if renting virtually nothing) and what you are willing to do (if you 'own' much of the expense of effective treatment not only can't be recouped on resale it will actually reduce the houses resale value, except in very specialized markets) and what you can afford
in trying to understand what actually works the library is a much better friend then peer to peer forums, if you want to understand . . . the forums can be a resonable place to refine and clarify information derived from books on theory
and at times be excellent sources for cost effective ways to implement specifics
but just one of the things to keep in mind is that while something little thincker then a sheet of paper (.169 in.) can be used to deflect (or absorb) 20 kHz waves, a 100 Hz wave requires a thickness of 2 ft 9 and a half in. to accomplish similar effect. Of course it is not merely thickness but density that effects how a wave will interact.
there are some things you can do, generally speaking while strategies are consistant each room's requirements are a little different but a lot of the basics have been discussed on this formum (as was suggested reviewing studio building forum would be a reasonable place to start) reason for this post is just a gentle reminder that if a solution to this perenial problems seems to be to easy it probably, at the very least, is effective only in a specific location and does not point to a general strategy
if room treatment were 'that' easy discussions would be relegated purely to fashion debates, i.e. which color of foam worked best
