Thanks!
I was actually using my kit lens - a 28-90mm that has a macro setting on it. Then I added 2 macro filters that I own - a +1 and +2. I was handholding at ISO 400, 1/160, and f/5.6. Took me about six consecutive shots to get one in focus and I had to do some noise reduction in PS.
Hope that helps. I'd love to get the 100 2.8. Good luck on that!