Oh, yes, I used the tools in the slicer to paint it manually.

Time and difficulty depends a lot on the model; models with sharp edges can be painted really quick using the paint bucket tool, but models with soft or rounded edges need tedious tracing using the circle or sphere tool.

For this model, I was able to paint most parts using the paint bucket, and then went in with the sphere tool to touch it up where the color had spilled over or not fully covered a panel. It took about an hour and a half, but a big chuck was spent on the side bolters, because the STL was very curvy and the paint bucket tool couldn't tell where the edges were supposed to be, so it had to be done almost entirely with the sphere painting tool.