I'm told that slides and negatives are best done on a high res drum scanner, but from what I've seen, prices for decent ones start at about a grand.
I have what is now an old Epson here that came with a slide/neg scanning set up. It's fairly high res and will do more than one at a time (IIRC, about
4), with halfway decent results.I think the best way is one of the slide duplicators that you find on Ebay. Most seem to run about $65-$80, attach to the front of the camera lens, and let you adjust, fiddle and otherwise play with the various camera settings and lighting schemes until you get pretty much what you want, at which point you just run a bunch through. If I didn't have studio flash, I'd use a halogen 250 watt light, adjust white balance and try it. I'd also shoot in RAW format if the camera had it, because that makes things much more easily adjusted, but RAW is a feature of DSLRs and higher end prosumer cameras mostly, and requires special readers for many programs.