It doesn't seem like you would have to parent it. I think that the best thing to do is to first load the character and the clothes, clothify the outfit, set up the collision object(s), calculate the simulation, then set up the final pose and calculate the simulation again. If you change the character's pose, you have to calculate the simulation again. BTW, for the first simulation you probably don't need 10 frames, I think less would be enough, it's just to set up the clothes. For the final simulation it might be good to experiment with how many frames you need. For example, I think that first I set it at about 20, but that wasn't enough for the dress to finish moving and settling down, so I increased it to 30. For animations, I would first set up the dress, then do the animation, and then do the final calculation of the simulation.