never really had any dramas with it, aside from it taking ages
generally if theyre played like shit, they sound like shit in which case its easier to just draw em in manually and use 100 percent sample replacement and use the gain tool to change velocities up. i believe james murphy even has macros for this specific purpose set to change things to 90, 80, 70 percent and whatnot, then slate does the rest by choosing an appropriate sample, which makes them not sound as fake.
otherwise, we also take the triggers directly in as clicks and use those to aid in locating the transients