Interesting post. Yes, making an emulsion is not hard. But those in the book "Silver Gelatin" which I think is an excellent reference are untested and there are many misprints there. So, tread carefully.
It is not generally known, but up until the time of RC paper, most paper emulsions were unwashed. The paper itself absorbed the salts and prevented crystallization. Film emulsions MUST be washed or you get a tacky surface with lots of crystals.
KI is added to increase speed and contrast. It can be added to the salted gelatin or after the wash step. THIS depends on the desired effect. Other addenda are also useful such as Rhodium Chloride and Cadmium Nitrate. It depends on emulsion type.\
This just reinforces the comments in the above post.
That mean, I have to wash my emulsion when I add Potassium Iodide?