Simple but takes time.
You need to take a flashlight with each match, the best option.
The other option is to find one from a chest but its much faster and better to just take a flashlight with into the match. Focus on just unlocking flashlights in the bloodweb for this. Doesn´t matter which quality, they all work in the end. My favourite addons are two accuracy leather straps, the better, the better for you. Some killers, their hitboxes are messed up and are either above their head I think, as some you aim at their face and it doesnt trigger. It may just work too, as I got on progress despite no sound notification, so just keep trying. Most killers will become aware that you have a FL with, so you need to catch them offguard, like when stunning them or they breaking a pallet. You can also get them when they chase you in a straight line and have distance, but it is hard and most killers will look upwards or down and approach you to avoid the FL beam. The trick to this achievement is simply repetition. Doing it over and over and you will eventually get it done. At exit gate, if killer comes around corner, you can usually get them with the beam too, but its rare you both are in that position.