Plastic gallon milk jug with lid, clean and dry
2-liter soft drink bottle, also clean and dry
HOW-TO (the hard part)
Cut off the bottom 2/3 of a 2-liter bottle to create a funnel. That's all.
The top of the 2-liter bottle is the funnel. Position it inside the mouth of the milk jug and use a measuring cup or empty, clean cottage cheese carton to transfer the seed from the original bag to the milk jug. You will need 4 milk jugs for a 20# bag of thistle seed. Put the caps back on the milk jugs to seal them from moisture.
To refill your feeders, just take a jug of seed out and pour the seed into the feeder, just as you would fill a glass with milk.