Chris,
I have on very rare occasions had to do this using 'conventional' pre-sprays but have not had to do it with micro-splitters, except when dealing with certain hair products, where I will lightly mist with Eco Spotter immediately after the standard product. A single agitation is then used for both pre-sprays.
Because of the way that micro-splitters work there should be no need for a 'second hit' once the 'splitting' has occurred the change to he soiling is permanent, so a second application should theoretically have no further effect.
I suggest that you may need to examine the way in which you agitate. On heavy body contact soiling it is often beneficial to use either a micro-fibre mitt or cloth, or a terry towel instead of a tampico brush. The towel can be lightly pre-dampened with the pre-conditioner to avoid it prematurely removing that which you have directly applied to the fabric.