Start with a very sharp filet knife.
About 1/2" from the tip of the keel bone SLICE through the skin only (not stab and puncture) to just above the vent. Then slice off to either side of the vent, forming an upsidedown "Y" with the cuts ending just below the vent. I go for about 1/2" away from the vent. Connect the tips of the "Y" with another slice through the skin. This take 4 slices and about 5 seconds with practice and a sharp knife.
With the tip of the knife, slice through the mebrane below the skin to reveal the guts. Follow the same "Y" pattern. You may just need to start the hole and just tear the membrane with your finger. Pinch the vent with your thumb and forefinger, pull out a bit, then reach in and scoop out the guts with your other hand. Just reach in and get it done. If you do this right, no poo will come out. If any does, just rinse very well. Poo is a part of process, especially if you didn't make your birds fast 12 hours.
You can remove the lungs by scraping them out with a finger, or by using a tomato shark (google it).
If you take longer than 2 minutes to do all of this you are either being way too timid, or way too squeamish. Just do it. After a few I can get this done in about 15 seconds each bird.
Take off the head, then cut the feet off, sort through the guts for the liver, heart and gizzard.
Rinse well, let rest, then cook and eat.