So in my use of "first order" what I meant was - what do you want the skin bump to look like? The idea that there should be more of the big wrinkles in some places and less in others, and that we have two nodes producing different size wrinkles, and combining them with a mask to control where to place them, etc. is the first order issue.

Choosing a Math:Add node to literally add the two effects is implementation detail and once you realize you need to add two nodes, there's no thought behind choosing the add node - it's your only sensible option.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)