Re: Which generator do you recommend ?
It's odd to me that you'd want a manual timer instead of a circuit automatically shutting it off when the desired strength is reached. As the silver electrodes are used up, the automatic circuit will compensate and make the same quality CS, batch after batch. With the manual timer, you'll have to figure out how much longer to run the generator as the electrodes become smaller.
For many years, the most highly regarded units in the online CS community are the SilverGen and Silver Puppy. The wishgranted.com unit is also good, but in my experience, a stirring mechanism must be added in order to make the best quality (polarity reversal is not enough.)
Argyria will not happen with properly made CS unless obscene quantities are consumed, and even then, it's likely to be a very mild case. The scary blue horror stories are all cases of CS being made with tap water, added salt, etc., resulting in a highly concentrated silver soup.