I make most of my rubs and in the process no matter how I try, end up with clumps. Mostly small and not great in number but annoying; when it comes to dispensing from a shaker.. Now I have the answer.
I use a 7 1/2" diameter stainless steel colander. The magic is it has 1/8" diameter holes in it..When making a new rub batch, it is run thru the colander. Anything that doesn't make it thru is ground down
using a mortar /pestle... I have sifted rubs made pre-colander using this method so now all the rubs exit the shaker easily right to the very end... For you Canadians: This is a Dollarama item. $4.00.
Added note: I don't use a grinder to process what doesn't go thru the colander as I don't want a super fine rub, especially the salt.