As the others suggest use the bag over your racking cane.
I've dry hopped in the keg a couple times and had good results. I used a hop bag and put some sanitized marbles in it to keep it down. the bag still floated with an oz of pellet hops and 4 marbles.
Fermenter 1: Gumball head clone
Fermenter 2: Azacca Mosaic Promise-ish