There was a thread here not long ago comparing the different brands of selenium toners. The consensus was that Kodak, Ilford and Adox behave very similarly if not identically.
I would start with a rather weak dilution, like the 1+19 mentioned earlier, and see if you like the results. You can simply tone the print longer or increase the strength of the solutions (by adding a bit more concentrate) to get more change in image tone, although the MGIV doesn't seem to change that much anyway. Keep a wet, untoned print nearby in the same light to compare to.
Since you are just starting with selenium toning, maybe my procedure will be of value. I keep two jugs of selenium toner, one strong, one weak and use the one needed for the type of paper and amount of image change I desire. Different papers tone more quickly than others and show more color change. I tone visually, i.e., I don't do time/dilution but rather watch the print till it reaches the desired amount of toning. This is different with different papers, subjects and even different amounts of contrast on VC paper.
My work flow is as follows: I usually print and give the first fix, then wash and dry my prints. Do wash and dry; keeping prints wet for a day can cause the emulsion to separate from the base. I then choose those I wish to tone and do a toning session later. The toning session consists of: 1. water soak - minimum 2 minutes 2. fix two (I use rapid fix 1+9 for 2 minutes each bath) 3. toner; the print is transferred directly to the toner without intermediate wash or rinse. This only works if the fixer is not too acid, otherwise stains can result. Any alkaline fix or the "paper dilution" of Ilford Hypam or Rapid Fix will be fine. Don't do this with Kodak powdered fixer. I tone to desired image change. 4. wash aid, 10 minutes with agitation
You could give both fixes, wash and dry, and then just soak your prints prior to toning. If you get discoloration this way, however, you may want to try going directly from the fix to the toner like I do, even if it means changing to a more appropriate fixer.
Also, I strongly recommend not discarding your toner, but rather replenishing it with small amounts of concentrate when the toning times get too long. The working solutions can be stored almost indefinitely; I have two gallon jugs that have been going for at least 8 years now (more likely 10+ years) and tone just fine. The toning solution needs to be filtered before use, as a black precipitate often occurs, but this is easy; a coffee filter in the funnel and you're set.
Reusing the toner instead of discarding it prevents the toxic selenium from being introduced into the environment. Even municipal water-treatment plants do not deal well with heavy metals. Plus, it is more economical and, as a desired side-effect, the solutions quickly lose the annoying ammonia smell and are more pleasant to deal with. I've been on my soapbox about this for some time here now, so a quick search on my name will turn up more info.
As mentioned, I have been doing this for years now. My fiber-base prints all test excellent for residual hypo and residual silver after two-bath fixing, toning in replenished toner, a 10-minute wash-aid treatment (HCA or equivalent) and a minimum one-hour wash.
Oh yes! Use gloves (nitrile are nice) or tongs to handle the prints while they are in the toner to minimize skin contact. Selenium is slightly toxic; no use taking chances. That said, I put my hands in the toner occasionally for one reason or another (to agitate a batch for example), but try not to do it too much.
Hope this helps,
Doremus
www.DoremusScudder.com