Best way to separate pinch welds

Blair, Keysco, and Rota-Broach are 3 popular brands.

Rotobroach is made by Blair. I use rotobroach cutters. Once you get the hang of it they take no time at all. I use them in a cordless drill on slow speed.
Sanding/grinding the weld down on the sacrificial side works great but is rather time consuming.