The process for each painting differs slightly depending on the level of detail. As an architectural designer I have a fond appreciation for materiality and small details when it comes to drawing and rendering homes or businesses.
While render techniques vary from building to building, the general process is similar.
I sketch a photograph of the building in question using a lead-pointer with varying line-weights, followed by water color, an acetone transfer, and then creating depth with ink and charcoal.
For portraits, pets, and landscapes I tend to lean heavier on the water color and sketching to capture the reason the picture was taken in the first place, that emotional attachment one has to their favorite pictures of their favorite things. Often these are more vibrant and heavier on water color.