For folks who haven't ever really gotten into painting, washes are extremely forgiving because they can be wiped away when you make a mistake with them, and they way they flow tends to help you get the effect you were probably after anyway.
This isn't a beginner video, but it kinda shows you how to think about applying these things and what you can do with your layering. Model paints work the same way (as do other paints—but the scale of model paints makes it more apparent.
Since he's painting furniture … this might be particularly useful if you're replacing or adding to the cardboard furniture, or planning to get the new reprint with sculpted furniture.