[Tropi]

Lotus
Nuro has posted several items on his track, but the best way to see all that he has done is to look in SF Resources
Cologne Raceway - Ongoing Developments
I think the whole story, to date, is there and a very comprehensive story it is too!

I would recommend anyone who hasn't already, to take a sightseeing tour through our resources - there is an ENORMOUS amount of beautifully illustrated information there, in addition to what you see on the forum pages.

SlotForum Resources

SF Resources are where Nuro And Swiss Racer, with the help of others, put in a huge design and development effort and the results are truly a tremendous credit to their artistic talent and sheer hard work.

 

[Tropi]

What a bunch of great pics in this thread - wonderful stuff!
A similar process from my model train days was to mix powdered glue (Cascamite in my case) with the ballast, lay it completely dry to the chosen shape and thickness and then fine mist spray with plain water. This worked pretty well too.

An interesting, slightly obscure detail was that using scale size ballast always made the particles look too small in 'N' gauge and that it always looked better if the particles were 2 to 4 times scale size. If memory serves, N gauge is 1:160 or so. I'm not sure if this same optical effect still happens at 1:32 scale. Luckily, being in the contruction business, I am in a position to obtain any size aggregate I want - just grab a shovelful of crushed rock dust or sand from a stockpile and throw it on a machine which will sieve it using any sieves I choose!
One drawback, as already mentioned - real sand and stone are extremely tough on paintwork in crashes!