Cold crash for a few days till everything looks clean. I say screw the beer gun. Sanitize and freeze the bottles prior to bottling. Then take a party tap and some tubing, forget the size because it has been a while and I have mine precut but it fits right into the cobra head and tight. Then pull the frozen bottle and fill. Gonna lose some in overflow but cap on the foam and you are good. The freeze will keep the head down and they will say carbed indefinitely. There were several articles and a youtube video or two on this method. Save you some cash or you can drop the 50-60 on a gun and deal with all that mess. Good luck.