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: IPA
Keg1: 15 Min Pale Wheat
Bottles: Brown Biscuit Ale - SafeAle S-04 / Brown Biscuit Ale - Abbey Ale Yeast II