Nunu Advice?

So I've been jumping back into more jungle play and playing some Nunu again bc I just love Nunu and I'm still at a rank where if you play something well enough you can win with things that aren't particularly strong/meta right now. Wondering about runes and masteries.

I've been running attack speed reds, flat armor yellows, flat cdr blues, and move speed quints with 2/21/7 masteries. The flat armor and 10% cdr help me stay at max hp while clearing the full jungle top to bottom side on first clear for level 4, and help with taking dragon as soon as the clear is finished (smite raptors to make sure I'm no seen going to it, level 2 consume, 1 in w and e, pop potions and solo dragon between 4 and 6 min in). Attack speed reds seems like the best choice to help w/ clear speed and lvl 4 dragon, but I'm not sure. MS quints and masteries seem good for counter jungling and kiting, plus allow ganks more often, and the 10% cdr on smite seems more useful than anything else for clearing which is nunu's strong suit.

Is there something I should consider for runes and why? Assuming 21 defense is the best (can't see why it wouldn't be as a utility tank champ), is there anything useful about putting the other 9 points somewhere other than the odd setup I'm using?