Converting pure nylon salt to polymer?
The problems with reacting pure nylon salt are as follows:


The molecules of hexamethylene diamine (HMD) and adipic acid will have a very hard time accessing each other's reacting groups, because of limited mobility within the solid structures.
The reaction is a condensation, so it will produce a substantial amount of water anyway, so pretty much any reason for keeping the reactants dry is irrelevant, because the final polymer will end up wet anyway.


It might be possible, but because of (1), your product might be impure, containing a lot of small unreacted adipic acid and HMD particles.

Also, If you don't want to deal with the tedious procedures above, considering that they were probably written for industrial applications, consider using this procedure. It's a lot more lab friendly.