SFX isn't "true" IR film, so you should be ok. I treat it just like HP5 or FP4 and it doesn't seem to cause it any trouble.
If you shoot it without the IR filter then it just turns into 200ASA B&W film. I've used a couple of rolls with varying degrees of success, I suspect the latter didn't work as well because I couldn't remember exactly how many stops to allow for the effect of the filter.
My usual technique (on a Pentax KX as it has MLU, B and a cable release) is as follows:
Set camera up on tripod without filter, compose, focus, set aperture and note shutter speed suggested by your meter/eyeball. My best roll was mostly shot with an SMC Pentax 28mm f3.5 at f16 or so, as that gave me huge depth of field to help out with the next part.
Reset focus for the IR mark on the lens, add filter, knock shutter speed down by correct number of stops (which on this body usually involves B, a cable release and the second hand on my watch to time it). Pull MLU lever up and check film advanced.
Trigger shutter with cable release, holding it down for as long as needed.
Shoulder tripod, walk to next location, repeat!