I used Sobo craft glue (diluted 50/50 with water and a drop of dish soap as described above, plus I wet down the coal with isopropyl alcohol before applying the glue) to do the tender coal load for my live steam K-27. As a finishing touch, I dumped the leftover coal dust over the top of the coal load after the glue was dry, then shook it off. That gives the load a naturally realistic dirty texture that hides any sheen from the glue. My coal load hides the butane tank and the R/C gear so it must be lifted out for access every time I run the engine, and so far it has stood up to a couple years worth of handling in all kinds of weather.