I've worked a bit in both of these industries as well as industrial access, mountain rescue and rock climbing. What I say probably wont apply to you guys in the states because I'm living in aus.
I started my roped career about 15 years ago and it was all high ropes instructing (outward bound type stuff), rescue work and teaching climbing and abseiling. We started with the real basics like body belay abseiling, building belay breaks out of karabiners etc. It's pretty much unheard of to use friction hitches in climbing and abseiling and not ever done in rescue or industrial access.
I'd lump window cleaning firmly into industrial access. In aus, that's a pretty heavily regulated industry in terms of insurance, accreditation and standards on what can be used and how. The short of it is that you dont have the gear, the long of it is that it may not really matter. It's all done on devices (gri gris, or racks with a shunt mainly) and jumars. 13mm is the standard rope size. Anchoring standards are pretty tough. Less and less of this sort of work is being done on rope. There's been a move over here towards pre-made pre-certified anchors at $300/go. To get contracts you generally need insurance, the get insurance you generally need certification. You may also need this to get the council permits required for diverting pedestrians off footpaths.
This doesnt mean that you cant just do it. Plenty of guys do. Lots have no insurance, or just general public liability that doesn't cover them for this type of work (but looks official enough to get work). If you don't have insurance coverage, then you dont really need certification, and then it's up to you what gear you want to use and how you use it. The consequences if any will also be all yours.
If you go down this path, have a few goes at simply descending the building sans bucket before attempting the job. There's nothing to hold onto on the side of a building, and only limited scope for moving side to side unless you start getting clever with rigging. You will want clever rigging otherwise you will only be able to clean one or possibly 2 windows wide on each descent. That could be a lot of descents. I've often used a barber hauler type arrangement as used on the jib sheet of a yacht for sideways pull.
You may find that you will want a bosuns chair (almost all window cleaners use them) and tie all your tools to yourself so you cant drop them. You will drop them. You dont really need ascenders, just a good locking descender and a seat.
The business of actually getting the windows clean isn't exactly trivial either.... have a few goes at ground level before attempting it on rope. Best of luck!
Shaun