You add white to process colours and you will end up with pastel shades.
You will figure out these process colours won't cover worth shit, and their intensity or shade is entirely dependant on screen mesh, number of passes, etc - you can't really tell a process colour until you print and dry it.
I'm with Mr. Frank, get a pantone book and cross reference the colour, and use your opaque base colours to try and hit what you want.
Use the process colours for enhanced colour mixing.
One of the problems with trying to mix to a 'CYMK' colour by using the 4 inks is they are actually talking about a laydown of 100% magenta flood, 100% yellow flood, 28% and 35% screen of the other colours, not percentages in a mix. One on top of each other. If you mix them together in a bucket, you get mud.
Remember too, CYMK or any process/multicolour halftone duotone shit is only a pale approximation of a full on colour.
Just my opinion, for what it's worth. So are all you clowns going to be at Flatstock in Seattle? Do they have beer?