Turning a globe into an equirectangular map can be done by hand too. Been thinking a little about it as I'm planning to do something similar… sometime… in an undefined future…
I think the easiest way – at least if the globe only has rough shapes on it – would be to take a paper with 1:2 dimensions, and draw one line in the vertical middle and one in the horizontal middle. These are the equator and prime meridian. Each important point on the globe is then transferred to the paper, using 1 degree = 1/360 of the paper's width. It'd be time consuming, but not actually hard, and if I've understood the equirectangular projection correctly it'd give an exact map and not an approximation. The equirectangular map can then be scanned/photographed and turned into other projections using G.Projector or something similar.