Ballast blends for the Milw in N scale

[TinyTurner]

I am looking to make an Approximation of ballast on the Milw for N scale, blending from readily available crushed stones.  There are are a good few sources of tiny rocks online, a recent discovery is

https://www.amazon.co.uk/dp/B0D5RB4HQH?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1
And Noch, Busch ect.

I am aware of ARM goodies that suit the midwest
https://www.armballast.com/product/1270b/

But the practicality is prohibitive (it's a long way to ship a bag of rock) but might get a sample bag to match.

Going through a few articles right now, learning:
It's grey
It's granite (or cinders depending)
Some of it is river stones
East = good ballast
West = bad ballast
.3mm is about right

N scale ballast usually isn't and scales to the size of boulders, that won't do.
So any of those Amazon colours even close?
What's a good way to go about blending?

[Ed Kapuscinski]

Go to your home improvement store of choice. Grab a selection of gray sanded grouts. Keep notes on your blend until you find something you like.

https://conrail1285.com/n-scale-ballast-using-sanded-grout/

[TinyTurner]

Yes! Will do. Just got a copy of Lance Mindheims 'scenery for modern layouts' that uses grout.
It's interesting stuff.
Kind of bewildering at first with so many brands available.
I can see it now. 
Sales youth: Whats it for, sir? 
Me: It's for my trains.
long stares 

A blending diorama is a good idea.

[nkalanaga]

Or, if you can find the right color, common mortar sand.  Much of the Milwaukee main in Montana didn't have "ballast" at all.  It was all river rock, whatever color the local rocks were.  One source I read, if unknown reliability, claimed that the railroad didn't like sharp rocks, because they wore the ties out faster.

On the other hand, by the 1970s, good ballast would have been wasted on the Pacific Extension, because the track wasn't good enough to need it.

[TinyTurner]

Sanded grout seems pretty rare here, but there is plenty of non sanded.
It seems to usually be a one part formula.
Mapei UltraColor Plus seems popular and is readily available in lots of useful shades.
I might just be missing something and it's already included and not mentioned especially. 
Could sand be added for the texture?

[nkalanaga]

Probably.  I've never used grout for anything, so have no experience with it, but have added sand to common patching plaster for scenery work.

[TinyTurner]

Having recently received a copy of Lance Mindheims book, scenery for modern switching layouts, I messaged him and he was very kind to say that using grout for our purposes, it does not really matter too much which one. 
I have a 'mud' colour sample coming and will see how that goes with texture.
I think a combination of the two would work quite well, filling in larger areas in yards, ect.