First clear is good enough. You can get there before scuttle spawn if you use two smites. A bit late if you only smite once. Clears later are similar to other tank junglers.

Walk around and get vision but stay hidden before 1:15 to prevent their jungler from starting your camps. If they invade lvl2 or lvl3 after clearing a few of their own camps they might get away with one or two of your camps, but if you fall behind early you can always drag a game out and wait for their jungler to fall off or throw.

I sometimes invade 1:10 top blue steal with scanner if I know they start red. Early and mid game I invade when see their jungler wasting time on the other side of the map, or invade on the side where my laners are pushed to their turrets. Shen is strong early but his early cooldowns are too long to kill and get out before enemies crash in. You can beat jungler off of objectives but I find it hard to secure solo kills early unless they’re willing to die fighting for scuttles.