lots of good advice above.
I bought one of those fancy bottling guns (the last straw), and i've used it exactly once. I have two methods for bottling depending on where i'm filling from and my mood.
One is using the poor man's beer gun, the tubing w/ the stopper installed. I took a spring-actuated bottling wand, cut off the valve/spring, cut a 45-degree angle in the end, and attached some tubing. That tubing fits snugly over a picnic tap, and it's easy peasy to use. It is in essence a counterpressure filler, and it works well.
The other is using a growler filler from a faucet. You have to get one that fits the faucet model you have. I have perlick 650ss faucets, and the filler just fits up inside the tap with a couple of o-rings to hold it.
It's not counterpressure, but after the first beer drawn, which cools the line and faucet and filler tube, there's very little foam.
As others have noted (yooper, for instance), cold is your friend. As beer warms, co2 comes out of solution, which results in...foam! So the trick is to keep things cold as you can. Many recommend chilling the bottles, which i do sometimes. If i have cold star-san, when i spray-sanitize the inside of a bottle with my vinator, it cools the bottle for me.
But once all the parts of the setup are cooled by flowing beer, i can even fill relatively warm bottles with little problem.
One thing i do like to do is have all the headspace filled with foam when i cap the bottle, i.e., i cap on foam. That foam is composed of co2 and beer, and not oxygen, so this is a way to purge the bottle's headspace of oxygen.
Here's my poor-man's beer gun; remember, the tubing at the top fits snugly over the spout of the picnic tap, sealing tightly and giving me a system that can handle the pressure necessary.
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