When you've got your partner in closed guard, The "Xande" Sweep can be a consistent go-to with low risk. However, your partner will often try to keep you from gripping their pants, in which case you might want to try to gain inside control with your shin in order to strip their grip and reset. If they attempt to stand up, you might consider switching to a Pendulum Sweep, but assuming they don't, a little timing may be beneficial. Watch where their head moves, and use this extra weight shift to execute the sweep. Consider using some Xande" Sweep Combinations if they're able to continue to resist.