I still bulk load film for the same reason old artists roll their own cigarettes after they can afford to purchase them by the packet. Nostalgia.
All loaders I have experience of work on a similar principle. Load the 17 or 30 metre roll in the dark, with the film end facing the light trap. It must release film in an anti-clockwise direction. The light trap pivots, with a slot through which film can be safely loaded into a cassette with the lid down, and closed to keep the bulk film light tight with the lid up. This is the fiddly part, the film roll is usually kept together with tape which has to be removed and the film end threaded through the slot... in complete darkness. You'll get finger prints on the initial frames, but they'll be on the unexposed end of your first film, hopefully.
Screw the film chamber down finger tight, and double check it is properly seated. Close the light trap - feel for it if you're not sure - leaving sufficient tail to attach to a cassette. Turn on the light or remove from dark bag. Light traps generally have a lid combined with a lever - if you can open the lid with the lever in a recess, you're good, but remember to open the light trap once you're ready to roll film with the lid down! Failing to do so will leave tramline scratches down the film, as it is forced over the sharp edge of the light trap.
A notched wheel engages with the film sprockets and advances the film counter. The "clicker" wears with age and the counter fails, but you can count frames, one per revolution of the handle. Mine failed intermittently recently, resulting in some very long rolls of film! Approximately 42 shots fit on a standard Paterson reel, some of mine consisted of 47 and in one case 52 frames. Surprisingly these developed perfectly wrapped round the Paterson spiral! Very long rolls can however lead to stress as torque builds up on the camera advance mechanism. Best keep to 36 - 39 max.