In vanilla sketchup:
-You can create a face in the correct orientation, texture that, set the texture to "projected", and use the texture from that to paint your model

with plugins:
-Pixero's UV Projection plugin might help you out here, it will speed up the approach I described for vanilla
-Marginal's UV editor could also work nicely, albeit with a little more effort
-I haven't used ThomThom's UV toolkit, but I believe it could present a solution of some description