Have you tried here?
https://www.rmweb.co.uk/community/index.php?/topic/33331-kernow-adams-o2/page/71/

Hi Rick.  Thank you again, yes, but I cannot find anything useful. Best wishes Kevin

Hi Rick. The real coal in the Loco bunker,  How do you fix it in place, bearing in mind that you may need to gain access to something “under the bonnet “ , and what about containing the dust?   Best wishes Kevin 

The real coal is a Woodland Scenics product which is secured with a gentle application (using a dropper) of their Scenic Cement.   That is diluted PVA so any similar mix should work.  It's non-dusty but cleaning the coal (!!) is achieved in the same way as all other loco cleaning namely with a puffer brush which - in my case - originated with a batch of photographic kit I inherited from a long-departed relative.

Hi Rick. Thank you for your reply. As it happens I have my own puffer brush, but, the “real coal” is actually REAL.Donated by a modeller of this Parrish, which I have been using to load wagons, no worries there, just layers of coal and super glue. Best wishes Kevin