When/how to add water additions?

Question in regard to water chemistry. When, and how, do people add various “additions?” I have gotten the impression in some of the things I have read that some additions do not “dissolve” into the water easily or on their own. True/not true?

For example - Let’s say I have 4 gallons of mash water and I want to add 1 tsp of CaSO4 and .5tsp of CaCl2. If I just put the additions into the water as it heats up to 165, and then stir it and dump my grain in, am I good? Or should I have made the addition differently?

The reason I ask is sometimes I see that “additions should be added directly to the mash” or similar phrasing - I interpret that as meaning it should be done AFTER the grain is added. Seems like it would be hard to disperse it evenly if this is the case.

So, does it matter how these (or other) additions are put into the mash?

Thanks

Chalk doesn’t dissolve in water and only partially in the mash, so it goes in after the grain. Gypsum, CaCl2, baking soda, and epsom salts are dissolve easily in plain water, so add them whenever’s convenient. Unless I’m working with a known recipe, I’ll usually take a pH reading before adding any salts - I’d rather not end up chasing the pH around.

I use Bru’n Water in advance to calculate my additions based on my water profile, and then mix in the calculated additives to my strike water in the mashtun before mixing in the grist, unless I’m using chalk, which goes in after the grist. It works fine because I have a few minutes where I’m stabilizing the strike water temp in the mashtun anyway, before doughing in.