No expert but maybe can shed some light on this in an inept manner... pun intended. An infrared film is nothing other than a film sensitive to the wavelengths of light that extend beyond the visible spectrum. In the case of ultraviolet light, that would be wavelengths shorter than violet. In the case of infrared, that means wavelengths longer than red. Violet on the short end, and red on the long end are the confines of what human vision can perceive.
A film on the other hand, CAN "see" wavelengths outside what your eyes can, and record them on the silver halide. To make a long story short, the infrared film can react to wavelengths beyond the humanly visible as well as to the ones you normally can see. If you wan't to record ONLY the infrared portion of the spectrum, you need on the one hand a film sensitive to it, and on the other hand a filter to block the rest of the spectrum: the IR filter does just that by letting only the long IR wavelengths through.
All this to say however, that you can use the IR film to record all the visible and the IR portion as well, and thus forgo the IR filter. A couple of considerations to bear in mind: IR wavelengths are longer than visible wavelengths. That means that focus at IR lengths does not take place at the same lens extension as visible wavelengths. If you shoot without an IR filter and thus chose to record all visible and IR spectra, you would need to chose which spectrum to focus on: IR or visible.
For EI and developing, it's very hit and miss. Of my sketchy memory I used to expose Kodak KIE at 200 EI without a filter... for development I don't recall but I thinks digital truth actually has times on it, or I could get off my ass and look through my negs to find times... FWIW, I like the result of HIE without a filter alot - and I'd recommend trying portraits.