Am currently waiting for some female Mexican Indica dom's to mature enough for pollination, but the males are pretty-much ready, and I just happened to have my camera handy. Thought I'd share some pictures to help members identify male plants. All shots are of males, and male 'nanners'.
On some female plants, the calyx can start-off looking like a male pollen sack. But if after a few days there isn't a pair of pistols (hairs) coming out of the pointy-end of the sack...likely it's a male. The nanners end up looking like a bunch of grapes, and will eventually open to look like a flower hanging upside-down. At this point (the first picture) pollen is being released. (you can see the pollen on the leaves below the flowers) Takes a week or two under 12/12 for nanners to start opening into the flower.
The last shot is of my windscreen. It protects the ladies from pollen releases, but you still have to pay attention, and collect as much pollen as possible, as quickly and carefully as possible. Been using this for a few years, with no problems.