I don't foresee any particular problems in the parts you're talking about, if they fit in the Taig's work envelope with enough room left over to get the tool where it needs to be. Cutting brass certainly isn't going to be a problem for it. It's not possible to estimate the time they would take, though, without knowing what size tool you're using and what the cut configuration would be. Usually your CAM program will give you an estimate, once you've generated a toolpath and specified tools and feedrates.
Coolant/lubricant can be helpful, although it's not strictly necessary with brass. For aluminum, it's more crucial, since it tends to stick to the cutter. But you don't need a fancy system; people often do this with squirts of WD-40 and a brush. Removing chips from the cut is important, though; recutting them is not advisable. Compressed air should only be used on them if you've provided an enclosure, since those needle-sharp chips can do a lot of damage when they fly around. But enclosures aren't that hard to build.
If you're using small cutters, then higher spindle speeds save a lot of time. The faster the spindle, the more material you can remove in a minute, assuming the machine has enough torque to spin it without bogging down. You'll need to slow the feed rate if the spindle isn't going fast enough to remove material at an optimal rate, but obviously this isn't going to make anything go faster. But if your parts don't require small cutters, then you can take heavier cuts with large ones and save some time that way. It sounds like the Taig would be a good starter machine for you if you're trying to produce small, highly detailed parts, but if you want to make larger, simpler ones, then one of those converted manual machines might work. I offer discounts on all the Taig tools, so let me know if you're serious about wanting to buy one.