My first try was not successful. This is what happens when you do not think and just follow what the tutorial says. I was trying to make polystyrene stairs look like ruins; aged stones. I ended up having nice & dark castle blocks. If you want to make a castle, you can try the following painting process:
I first gave the whole a black undercoat (acrylic paint). Carefully done this to not to leave any white spot. After undercoat was dry; I drybrushed the model with dark grey; not covering the black details.
After each color is dry, I drybrushed several times from darker grays to lighter grays hoping that I could get a better lighter look… But nope… I even added a gray blue at the end. Nothing helped… I decided to leave this alone for the day continue the other day starting all over from the beginning to the painting. Here is the tutorial if you like to check out..