A few things you may want to look into:
- Buffered papers can cause problems, odd color shifts, etc. Finding a good unbuffered paper will aid considerably (the lighter the better too)
- Have a negative with the correct tonal scale. Good negatives for salt should be nearly unprintable in silver even with the softest contrast grade.
- Avoid tap water in the first wash. Chlorinated water can have undesirable effects on your prints. After the print is toned and fixed, final wash in tap water is fine.
- Straight Hypo works fine without any additives. I normally use 1 heaping tablespoon of crystals to 1 liter (or 1 quart) of distilled water
- Toning (especially with a gold chloride solution) will help, not only with permanence but also with final color
- Rod coating is fine, but a good Hake, sable, or camel brush works well too. I've never had good luck with foam brushes.