I use a large changing bag, about 2' by 3' with a large plastic Tupperware-type box inside of it to give my hands some vertical working room. Then I open the film can and set both halves with the open side down. I put the source roll on one of them and the target core on the other and start winding. The key is to make certain that you handle the film by its edges and keep the dust out. I have done 2 and 1/4 400' rolls this way without any problems.