How do you portion out a large bottle of perfume or cologne?

Glass container only. You can find atomisers online. You can use a a pipette to draw up and dispense it into the new container. I deal with essential oils and fragrance oils. Leaving them in plastic bottles is bad. :/

Glass container. @cazzie is right. There are special little bottles with special little funnels. They have nice ones for carrying along in luggage or a purse that are metal or plastic outside and lined in glass.

Seriously, though, any small glass will do that is well sealed. Go small and well sealed so the air doesn’t get to it.

If you have deluxe samples of perfume you can wash them out thoroughly when done and fill with your favorite perfume for something small in a travel bag that you use up quickly if you just need a quick cheap solution.

Just put them in a small spray bottle or any bottle that is tightly sealed.

The local chain drug store sells the containers as well.