There are many ways Hemlock, and I find that pollen last a long time. Just dry out whatever you take and then keep in a tub or glass jar.
You can snip off the yellowing sacs that are opeing into a small tub or jar.
You can construct little paper funnels round the plant to collect the falling pollen.
You can snip off branches that are maturing and hang.
Or you can cover the who branch with a bag and shake....
well, it's really a case of doing yer best to collect as much as poss in as least a messy way as poss....I think snipping and collecting into a tub works well for me.