Hi Trion, it looks like you've got a fine machine there, as one who has lived with and around shapers for over twenty years, I would say you'd waste your time with central oiling, as was mentioned, generally, you oil it before you start, and unless you're pushing the machine such as using it for production line of a particular part, that's all the oil it will need for the day. The smoke issue is best controlled by the cutting fluid used, I like the smell of old time sulferated lard oil for steel, so I put up with the smoke and enjoy the aroma. The primary need for the different speeds is to compensate for length of stroke. I currently use a 7 inch Atlas while I rebuild a 12 inch that's from the 1870s, I generally use the two slowest speeds for pieces two to five or six inches of cutting length, but while cutting keyways in a gear, and with a stroke of 3/4 of an inch, I often get up on the second from top speed and I've had occasion to use top speed, out of four belt speeds, for very small parts which I use it on occasionally. As to keeping the bottoms of dovetail cuts even, generally, it is the outside of the dovetails which establish your plane of action, the bottoms are more for clearance, and they are usually put pretty close to the same using something like a cigarette paper to ensure the two tools are set to the same final height, or a shaper and planer gauge, used from the table as a base, and both tools set to it. Occasionally the inside of a cut like that is used for the locating surface, in which case the shaper gauge is the best answer, along with the cigarette paper, which I tend to use with setting up for milling, and for setting tools right on, in the lathe as well. I was taught that when I was about ten or so, and forty odd years later, they are still exactly one thousandth thick, and a cutter that tears the paper is touching metal, but not marking it, giving a perfect zero, plus or minus a couple of tenths, depending on the mechanic's sense of touch. I probably get a year or so out of a pack of papers, as I use them until they are shredded to pieces and disappear. They give me funny looks at the grocery store, but they don't know what I'm using them for. They are also of great use for testing the flatness of something on a surface plate, or testing to see if a part is pulled down equally in a vise, or if a corner lifted up from clamping pressure.
All in all, that is a beautiful find, and it should be a real workhorse for you, mine is, and I can't imagine working in a machine shop without one, having started off in shops which always had half a dozen or more, of all shapes and sizes. While you're putting it all back together after repairs and paint, take the time to make sure all surfaces are square and parallel, and take a cut off the table, as fine a one as you can get away with, there will never be a better opportunity, and they are very finicky if they are not right, from the start, but worth their weight in gold if they are. They make quick work of getting a flat seating surface, when that is what you need first, before you can do anything else on a part.
All in all, I hope you get as much use and pleasure out of your shaper, as I do from my own.

mad jack