I suppose a gas powered trash pump with a bigger discharge is probably the correct way to go, quicker but.....sump pumps are relatively cheap, you don't have to gas them up and you can't hear them running!
The discharge on mine is 1.5" and used the flat blue hose you can get at farm stores. You buy it in bulk or by the foot and put your own ends on it. I had enough hose to get me out of the pond and then shoved it in 4" flexible, corrugated black tubing that's used for drainage (cheaper and I had it on hand). At the junction of the hose and tubing I set it on top of a cinder block and tied it down to the block to keep water from running back out of the tubing. The larger tubing also helped reduce the velocity of the discharge water.
I placed the pump in the pond via a small Jon boat to get it as deep as the cord would allow. The cord on sump pumps are rather long, I think mine is 15' and I added an extension cord to that. If you have a dock this would be easier. I only had to move the pump once and this is important because it is a major PAIN getting out on the muck. We put down sheets of plywood over the muck (end over end) to push the Jon boat in and move the pump. Once the pond was pumped as low as it could go we used the plywood to get to the pump and dug a depression under it with a shovel, shoveling muck isn't easy either, to further decrease the water that was left. The pump stayed there until the job started.
There's more than one way to skin a cat and this is how I did it and I would do it again this way, it wasn't that bad. My pump still works great and I got it at a yard sale really cheap. If your going the trash pump route you could rent one if you don't want to buy but when you have a pond there always seems to be a need for a pump.
When pumping, keep in mind that the water level drops slowly at first and goes much faster the lower it gets.