Good for you RGS and thanx.
You don't want the film rewound as you'll need to clip off the exposed bit to get processed and if it is wound back into the canister there is no way to determine where the exposed bit ends and the unexposed bit begins.
The idea of testing the film this way is to save as much as possible for 'real shooting' and with this film it is important because the film is great stuff and it is nolonger made.
A couple more things use a tripod when testing, don't change the zoom on any given scene. You'll want each picture to be identical to the last with the only difference being the film's rating. When shooting skin make sure that the model's skin occupies about 70% of the frame or something in a little excess of Matt's example. Finally if the lab can do projection contacts those might work better for 135 as the frames are small. Projection contacts are where they put all the film in an enlarger and project them onto the paper. It still allows you to compare each frame put the frame size will be larger and therefore easier to inspect. The cost should be around 5.00 for processing and 10-15 for the contact.