CWret, misting with a water soluble coolant is a bit of a throwback, useful for HSS when milling, particularly in slotting, and to avoid using flood coolant which gets everywhere on a small Knee Mill. The mist also diminishes the air quality.
Acculube became popular with micro drop “mist “ of a vegetable based oil, minute amounts and very effective at lubricating, also messes with air quality. Works well on something like stainless if using carbide endmills or HSS.
Stainless requires lower speed and higher feed in general.
Larger indexable face mills in steel are okay to run dry, they are not ordinarily run at high depths of cut in a slotting situation , especially on low powered mill like an Excello. With lighter width (1/3rd of cutter width)of cuts the carbide is exposed to a lot of open air and has a chance to cool down or at least not build up more heat due to workpiece contact area.
A continual stream of air is useful for clearing the chips( enabling them to get into every area of the shop easier) .
The higher positive type of pressed chip control inserts generate a lot les heat and impact, the coatings keep more of the heat in the chip rather than transferring to the tool. I wouldn’t worry too much about coolant with indexable.
You seem to be okay on the drill end of it with the various compounds.
Both carbide and HSS endmills will survive without a coolant or lube if you pay attention to speed , feed , I wouldn’t mist carbide endmills, just air to clear chips.
It’s been mentioned before, we are not production shops, we have time and don’t need to push everything to the max.