I've always mixed my chemicals (for over 30yrs...).
- The difference between devs is not so big as it may seem. The Film Developing Cookbook will lead you in the right direction.
- It's more important to use a dev until one is fairly familiar with it before trying a new one.
- For papers it's the same - there are basically warm tone and cold tone ones, from there on dillution will cover about all your needs.
In the WEB, take a look at:
Re ascorbate devs, Patrick Gainer (he posts on APUG from time to time) has done a nice job.
Here's the start page for his devs: