I've used Zaino PC by hand to do motorcycle tanks before, but yeah, it takes a really long time and you don't get the luxury of choosing different pads. I've also used that and XMT 360 to clean fingernail marks out of door handles.
My friend did some spot correction on his truck with XMT 4 and a sponge made out of the orange pad material and said that worked pretty well.
You can get decent results by hand, but wont be able to remove the same defects that you will by machine. It's honestly worth the $150 for the machine to me in the better results & time/effort it will save you the first time using it. Once you get one you'll never even consider polishing a whole car by hand.. Plus you can buy brushes for scrubbing carpets and whatnot with it..