10 to 20 minutes? More like 8 hours for me, but I guess that kinda comes with the territory of maintaining a nearly 45 year old antique..
https://www.youtube.com/watch?v=sP2ZRLeRdR0
For me, a proper bicycle cleaning involves a 90% teardown and rebuild, including cleaning and regreasing every single bearing on it, including the freewheel. The only parts I don't tend to bother with disassembly are the spokes, unless perhaps one or more is broken or the rim is somewhat warped.