Its best to use the drop method, from my experience over a 4 hour period worked perfectly. Pop the bag in your tank open it up, I try to peg the bag to the side. leave it for half an hour to acclimatise, and give the shrimp a breather from the bouncy ride home, i also turn out the lights, and there after it is recommended one drip of tank water every 30 seconds there after, however I dropped about a quarter of a turkey baster every couple of minutes. Over 4 hours, Shrimp are more sensitive to the water change than fish so the slower the better imo.
Also try to drop some gravel or some leaves in the bag when they are acclimatising, this gives them something to hold onto and reduces stress.
Happy easter