You do not need high speed film for star trails. Star trails photography is not about perfection in imaging, it is just for a bit of amusement and interest, particularly if you get plenty of star trails and can research just what the patterns represent. ISO100, preferably reversal slightly underexposed, will be excellent. The smaller the aperture, the larger the number of star trails and the greater the colour shift due to reciprocity failure. Lens choice is a perrsonal one: the wider the lens, the greater the view but star trails will always be visible, and can be made even more appealing with a strong silhouetted subject like a rock, monument, old bar/building etc. My EOS1N takes care of star trails unattended with its intervalometer and usually a 24mm prime lens, no filter and most commonly for 2 hours before pausing for an hour and then taking another frame. For other cameras, f5.6 to f8, on bulb/time and shutter locked opened from 2 to 2.5 hours will give you a very good starting point. Be aware of your surroundings, roaming animals, people (either or both can trip on the tripod), the possibility of theft (if camera is left out in the open by itself) and cold: as the night progresses condensation can form on the lens and negate the entire experience. Above all else, have something to keep yourself occupied over a long period of time, or just leave the camera out, where it is safe to do so and retreat inside. And don't treat star trails as a critical science: it's not, it's just for fun.