My Diamond plate toolbox is a few years old and has some water spots on it that just don't come off with regular washing. Can someone recommend what to use to make it shine like it did when it was new? Like a polish/cleaner or something?

Try some metal polish, like Never Dull, try it in a spot that you can't see first to make sure it won't fuk **** up.

yeah that never dull stuff works great on my toolbox, and if you put a few coats of wax on it it usually won't get to many spots. It is just hard to put wax on and take it off the diamnond plate unless tou have a buffer.

do they have it at wally world and auto parts places?

also, why is it hard to put wax on/take off of diamond plate? is it because of the bumps and stuff? or the surface?

Yeah they have it just about everywhere the most common name is eagle one never dull and it comes in a lilttle metal conrtainer. as for the wax the only prob with taking it of by hand it that it gets stuck around the diamond curves so it takes a little more time to wax than a normal finish.