I used a pre-stain wood conditioner on a softwood before applying the first coat of stain. It looks good--much better in fact that when I didn't use a wood conditioner on another softwood piece. I want to apply a 2nd coat of stain to achieve a darker result. Do I apply the wood conditioner again on the already stained surface before the 2nd coat of stain or should I just apply the 2nd stain coat? The instructions on the can are confusing as to whether the conditioner should be applied again before a 2nd coat of stain. It might be implied in the instructions, but am not sure. I appreciate anyone's time with this question.

No... you only use it on the bare wood. It helps control the absorbion into the wood. You don't need to use it over your first stain coat, nor should you..

Smoothy X2