Apparently, older DSLRs do better with a lens filter. They are more sensitive to IR. Later models had better IR blocking. Good for IQ but not for special use cases like this.
Ideally, you want a body with a CCD sensor. The Pentax *istD line comes to mind. They are dirt cheap these days.
I have to admit that I have a *istDL and an IR filter that has seen little use. Time to get it out and try it again. My initial efforts were not great.
Here is one I made earlier. In practice, it is quite fiddly. First of all, forget about auto focus. Even manual focus is difficult with the filter on. I set the camera on a tripod, focused and reset to the IR marking on my old school lens. In this case it was an SMC Pentax 50mm f/1.4 I think (but my memory is a little fuzzy on it). I then put the filter in place and tried a few exposures until I found that that worked, more or less - in this case 1/6 sec, ISO 400 and f/11. One could pre-focus, I guess, but I have not tried it yet.