Using a powder flask is easiest for metering powder into the powder measure.
The spout top on the Pedersoli flask is calibrated to measure about 25 grains per fill for quick loading in the field, and is narrow enough to fit the mouth of narrow measures.
http://www.cabelas.com/cabelas/en/te...0006439212239a
However, the flasks with a push button valve are favored by many. Unfortunately Cabela's doesn't sell the Traditions brass push button valve model with the thin stem. But the TC U-View flask received good marks.
http://www.cabelas.com/cabelas/en/te...0006535212557a
Read the product reviews.