I used kitty litter...
Anyways, I popped off the caps on the inside ends of the bars, used a paper 'funnel' to guide the fill in a bit at a time, tamped it in with a suitably long bolt, and then added more fill, tamped again, etc. until the bar was pretty much full. At this point, I caulked inside the bar (to hold the kitty litter in place), replaced the cap and I was done. No removal of the handlebar was necessary for this.
I'm sure you could use a similar procedure for shot, I just didn't have any on hand.