For using bus service, the fastest (as stated before) is Pop to MK, Monorail (or launch) to GF.
If you go to Epcot, chances are you will have to take the Monorail to TTC, then resort monorail to GF.
If you go to D/MGM AK, or DTD, chances are you will get on a bus that goes to the Monorail resort loop (Comtmeporary, Poly, GF) Depending on the order of stops it could take more time.
If you miss the MK bus, a taxi would be your fastest choice. If you allow time, any of the routes will work, just allow
at least 60 + minutes. I would allow more, but then I like to walk around the GF.
Just noticed the
scooter in your post. If that is just for cute, please ignore this. If that implies you
need a mobility device, you might check with Disney and see what special accomodations they have for transport resort to resort.
Going on multiple buses can be entertaining (if you have time), sometimes we take the longest bus route just to "sight see".
Just MHO, YMMV
Andy