I like to add my clay to a small amount of soap at the time of trace, but I like to swirl my soaps, just for that little bit of 'pizazz' I add my fragrance at a light trace...... as for milk, yogurt, aloe, and those thing, I like to add them with my lye, I haven't had the opportunity to make beer soap yet, but it is on my list of soaps to make, lol!
Honestly, I think you have to find what works for you, and what you feel comfortable with. That is what I've done, worked with making soap for a while and tried a lot of different techniques, then went with the one or combination of, what worked for me.
Give a couple of options a try, before you pick and choose which method you like the best.
Hope this helps, at least a little, lol.