Jacek Bołochowski and his stunning work on his diorama Famo Rubenzahl mit Sd.Ah. 35 if you look carefully through the pictures I am sure you will pick up weathering tips, Jacek scratch-built a lot of this but it is now available link under the first picture where you can buy it in a paper model kit, however, I don't think will be too long before it makes an appearance as a 3-D printed version
This is partial text from the full article (usually with photos) at https://armorama.com/news/famo-rubenzahl-mit-sd-ah--35
