Like many others here, I use a 3D modelling program in my iPad to create simple assets for locations I use a lot. Then I set the camera at the right angle, take a screenshot, and draw over the top of them. It saves me hours fiddling with perspective guides, and it helps keep regular locations consistent in design.
If I need to make a background I don't intend to reuse often, I'll either grab a licence-free 3D asset and draw over that. If I can't find something with the right look, I'll just build something made of very basic shapes for perspective purposes, and freehand in the details myself.
It helps speed things up immeasurably! I can sketch backgrounds from reference and imagination, but it's a lot more time-consuming than using 3D assets. And time is not something I have in abundance.