For the headstock bearings use grease, as any oil will get flung out. My choice would be Molyslip, because I know it will last many years, and I have a can of it. For slideways of all sorts I don't usually bother with anything. If I was worried I'd use a good wax polish, which finishes up dry and is easy to redo once in a while. I do have some very expensive dry slide grease for the food industry that has a lot of PTFE in it, but I don't think it has any advantage for these machines. It's reserved for my visor (motorcycle) where it clears the rain really well.
Why use any oil when tapping? A good sharp HSS tap will cut steel perfectly well when used by hand. A cheaper carbon steel one might need some oil just to make sure it doesn't get warm and lose it's edge. I just use any thin oil I might have around. For cutting (in any way) the softer grades of aluminium WD 40 works well. I also use concentrated car screen wash. It just seems to help if there's some liquid on it. I suspect plain soap and water would do it.
The vast majority of the stuff I do on the Unimat is cut dry.
