Hi there,
Luckily Bessa's have metal shutter curtains, so I wouldnt think there would be any problem, just take regular precautions, a shaded area would be best, however depending on which Infrared film you are using, particularly Kodak HIE, which is very sensitive, you may get fogging anyway. I would just suggest shooting the each scene at least twice to allow for fogging, and I wouldn't constantly change lenses, as this seriously increases the risk of fogging.
As I expect you already know, a regular red 25a filter will give you the most dramatic infrared effect.
Good Luck