This morning I was doing some yoga for the first time in awhile, and I was reminded of this thread.
I was hinking about the function of the serratus
Just remember the serratus has 2 functions. One is shoulder upward rotation of the scapula (achieved by flexion of the shoulders above a 90 degree angle) and the other is protraction of the shoulder blades.
and realized that the sun salutations used for a standard yoga warm up

activate the serratus quite nicely in the transitions from up dog to down dog (poses 7 and 8 in that image).
If you're doing a more calorie intensive yoga style as cardio (like astanga or "power yoga") you'll be doing tons of vinyasas (also called 'hindu pushups')

That's basically a tricep pushup, followed by a stiff arm slide backward into the down dog positon (all shoulder).
Just convinced myself
more that yoga is a perfect compliment to a good lifting routine.
Well a pushup into down dog is a good serratus activation, thoracic spine extension, calf stretch or calf dynamic stretching if you alternate dorsi and plantar flexing your feet, and hamstring stretch down correctly. I'm not a huge fan of a lot of yoga poses because your lumbar spine gets put into flexion and extension or twisting constantly and this would especially happen if a student was unaware of how to properly move into or out of any given pose.
Pushup into down dog is indeed a great one though. Won't do almost anything to strengthen your serratus, but it certainly will activate it.
But... Do the really big n buff guys pay attention to train this one isolated?
I bet this one gets trained with lots of other compounds. Like OP.
It does get trained very well by OHP or stabilizes in many compounds BUT it's often woefully under-recruited, inactive or weak. It's like the glutes, often you have to make it "remember" what its job is before you can really get to using it or strengthening it in various exercises. I don't think you really have to isolate the serratus besides in activation movements, it should just be part of any good pushup, overhead press, etc. to use it.