Put your arms on his biceps and push a fuckermother.
When you back him up, sweep your foot behind his lagging foot as he is backpedaling while twisting him down.
Some pajama boys call this de ashi barai. But you know kicking a fools leg out can show up in a lot of situations.
If he tries to push back, then duck under to the back.
The added bonus being the fact that you're also jamming his arms, making it difficult for him to try and trow ands or pull something without you in control.
Alternatives or situational matters;
1. If you have space and momentum, double legs are, in my opinion and as a general rule, more reliable, less energy intensive, and less prone to shit going pear-shaped in weird ways than tunnel visioning on a single (in most forms). Hit a clean pickup and slam. Changing levels and shooting for a high dive bodylock, or coming up from the hips into a bodylock, is also functionally isometric for this use-case.
2. If you are in a phone booth or you (can) push the other guy into a wall, jam your underhook in and screw it up into a crossface/further underhook, head position to increase neck pressure even more, and get wrist control or bicep tie on the free arm, thus locking both his arms up, while leaving you free to knee him in the nuts (or body or inner thigh if you're not hardxcore). You could also throw him by fully to take the back, or hook the leg and twist/sweep him down, if you like.