You're using baking soda and not washing soda? Baking soda should not affect pH so much but washing soda will cause them both to rise substantially. Add the baking soda to water first would have no effect on anything but you really don't have to do that step. You can just add it slowly to the skimmer while the pump is running.

When adding acid, you do NOT add it to the skimmer. Add it in front of a return jet. If you have more than one jet, I'd say it probably doesn't matter which one you pour it in front of. I guess I'd probably go with the one that is the farthest away from the skimmer if it were me.