ORIGINAL: Rodney
The Saran wrap work very well, leaves an absolutely baby bottom smooth surface and allows you to feather out the edges by carefully smoothing them out with your fingers while the epoxy is still smooth and flowing. Let the layup cure completely (over night at least) before removing the Saran wrap and it will come off very easily. I do not know if other clear food wraps will work as well as Saran or not, I hear some do not release as well as Saran does after the epoxy cures.
Before glassing the mid-wing I did a control sample (learned this from Mythbusters) using the Saran wrap. I expected the wrap to have a smooth surface but it does not. There are striations in the wrap. I applied 30 minute epoxy to a test strip of plywood. The epoxy went on smoothly but when the wrap was applied the wrap could not be pulled or stretched to remove the striations. Once the epoxy set and the wrap removed the epoxy had taken on the exact imprint of the wrap. Maybe there is different wrap that has a smooth surface but the Saran wrap I used does not. So, I applied the epoxy with a old credit card not using any wrap. The result is a very smooth surface. If the wrap would have worked I can see that it would have given a smooth result.
Allan