I have always used the humalog pre-workout, but was told by a pro trainer that taking slin pre and post workout was the best way to utilize it.
Now, as mentioned in a previous post, depending on the time you train may dictate the best time to use the Humalog or Humalin-R.
For me, I prefer taking Humalog pre-workout (Mike Arnold's protocol), followed by Humalin-R post workout with a big post workout carb shake and my hydrolyzed whey. Within an hour from this meal, when the Humalin-R is kicking in I then have a decent solid post work out meal. Then another meal within two hours when the R is hitting for its final time.
I have only tried it a few workouts, as it was towards the end of a slin run. It worked quite well. I'm on days off now for another two weeks, but once I start back, I will be running it pre and post for a full thirty days, as mentioned above..
Time to get jacked!