Barry, I'm not really sure what you mean by 'brown better/quicker.'
I think I'm being confusing with my usage of the term 'brown' here. It's confusing because good cheese will bubble and eventually brown, while bad cheese will quickly brown on top and burn. 'Brown' can be good and brown can be bad. Let's move away from the term. The same way that, if you crank up the heat on pizza, you get uneven black spots/char, lower fat cheese will brown quickly and unevenly as well. We need to differentiate between the kind of horrible cheese 'blackening' that forms on the top of low fat and/or garbage cheeses that doesn't melt/bubble right and just burns on the top versus a good high fat cheese that, over a longer time, will bubble and take on a darker shade of tan. Cheese blackening = very bad. Cheese tanning = very good.
If it helps at all, ignore the color completely and focus on bubbling. High quality and fattier cheeses bubble better. Low quality and lower fat cheeses have trouble bubbling. Bubbling makes or breaks a NY style pizza (unlike Neapolitan where bubbling is generally a fault).
Within this context, here is the answer to your questions:
1. Whole milk part skim will bubble/tan better than part skim
2. Tossing part skim with oil will promote far better bubbling, but, it can get a bit clumpy. Drizzling a very light layer of oil is preferable- or spraying is even better if you've got a good sprayer. I don't really believe in either Pam or Pam clones, not even the 'natural' versions.