I get told I should stretch all the time. I have access to tons of foam rollers, bands, etc. I really just don't feel like it makes a huge difference. I'm pretty sure the people I know who tell me to stretch a ton are barely mobile themselves. The only day I absolutely warm up is bench day, in which I do tons of face pulls and rotator cuff movements. But I only bench 290 so what do I know. Squat and deadlift day I just make sure my hips are plenty flexible by stretching them apart a ton.
But as to getting your blood flowing....eh.
"Does a lion warm up when he's hungry? 'Uh oh, here comes an antelope. Better warm up.' No! He just goes out there and eats the sucker." Jack Lalanne
But personally, I can't really see how training your body to have huge mass would be in line with having mobility to begin with. This one always escapes me.