There are many ways to finish a double leg shot. You can sweep them off their feet in one motion (the classic double leg), you can lift them up and slam (think Matt Hughes), you can trip (think Pablo Popovitch and Marcelo Garcia), or you can sprint and run them over. Each of these finishes requires a different key attribute: timing, power, speed, and hustle.
I like the sprinting double leg because it is always there for you. You just need to hustle. So if you are missing a step with the other finishes, then just take a few more steps and go into a sprint. 🙂