He uses paint, but the parts he uses are probably very small, with a saucer probably consistin out of multiple components, and being compressed in size. Also, he knows how to bend and bow the proportions of these parts very well. Also, adopt his colour palette, and try to deduce the parts from what you saw. Try to make a kit of your own of neccesary to familiarize yourelves with kitbashing while mastering it as well.
As for sketchup, it is quite good, and RICK King AIFD, Borgman and some others probably use it too. Try to render the models in kerkythea, an advice that will be confirmed by Borgman.