Are you playing on pad? With Stick it is super easy in any decent connection. Local play even easier then the hit stop option selects from sf4. The key is as soon as you input p for the pot buster, immediately smack p k s. After about 5 mins in the lab you should have the rhythm down. It is really worth learning, Once you get decent with it, then you can add heat to the end. If done quick enough, if you get the yrc (opponent jumped), heat will come out and catch them. This isn't a perfect option though since alot of characters aerial normals on jump or jump back will beat heat, also does nothing to catch backdashes.