I recently digitized several hundred slides using a bellows outfit with a slide copier attachment on the end of it (essentially a slide holder and a diffuser - not unlike those on the ES-2). OK it's not actually a Nikon ES-2 but it is an earlier and entirely similar concept. I found the system worked very well indeed and in particular once set up (finding focus, working the bugs out of your workflow etc) it enabled really very rapid copying of slides as once you were happy with the set up all that was necessary was to remove one slide and put the next one in, then repeat that as many times as needed, slide after slide. All settings on the camera remained the same for each shot unless I sensed that a slide was dark and needed a bit of additional exposure for example, in which case I just moved the exposure comp dial for that shot then back again afterwards. As the slide holder, lens and camera are all locked together and the resulting system was also on a tripod, exposure time was not critical in the sense that there was a risk of movement so I was able to stop down the lens to f8 or even f11 for maximum depth of field (just in case the slide / negative was not entirely flat) and shot using exposures like 1/8th of a second where necessary. Also as everything is locked together there was no need to use a cable release or anything of that sort as camera shake was not an issue in this set up.
As to lighting I just used a cheap ($20) LED battery-operated work light bought from a big box hardware store, set about 30cm behind the slide holder. I wondered if the light would be even enough but it was because the slide holder I used, like the one on the ES-2, has its own built in light diffuser. The work lamp had switchable light colors - pure white or daylight color but this is not critical as the camera white balance will handle this OK.
I have some more still to do and the only refinements I plan make for the next batch are two: First, I plan to shoot tethered this time. It is a convenience to be able to immediately view the resulting image on my PC. With some tethering systems a live-view can also be seen before the shot is taken. I am not yet sure if mine can do this but if it can I will use that feature also. The second refinement is that because I can view the resulting image in larger format and at higher resolution on the PC screen it will allow me better to assess its exposure as well as if there are any other problems. If needed I will reshoot with bracketed exposure setting on the camera engaged so I can merge the resulting shots afterwards in post. This should help deal with contrasty situations.
That's about it. If you are like me you will no doubt find that it's much more of an effort to deal with the images afterwards in post. Most analogue slides were not as sharp as we are now used to, so tweaking that required considerable effort with at least some slides (though of course it can never be fully dealt some adjustments can be made to improve
apparent sharpness.) The main problem though as always when dealing with old slides is cleaning up scratches, dirt and dust on the image with a cloning stamp or similar tool. That takes time but even that, I found to be not too annoying and over all I enjoyed the process mainly because I got some results that pleased me.
BTW shoot in RAW at maximum quality. It gives you best chance to work out any problems in post. And while you are about it, also shoot at your base ISO setting to minimize any digital noise in the image. Noise is seldom much of an issue with most modern mirrorless cameras but its better to avoid the problem given you will almost certainly have to deal with some problems with sharpness anyway due to the inherent nature of analogue film and slides so the more you can do to avoid anything that will soften the image further the better off you will be.
I put up just a few of the shots on Flickr (most of which were converted to black and white in post). Examples here.
https://www.flickr.com/photos/life_in_shadows/albums/72157719320330456
