I vaguely remember that the Wash. Mnmt. trick had to do with a slowly rotating audience platform with an arch at the front. But I never figured out the jet trick.
I think the jet trick was a variation of the rotating platform, but I might be wrong on that. I think most of the times they do a "really big thing disappears" trick it is some variation on the rotating platform. I'm not an expert on magic, maybe some Freeper/magician can offer more.