Heres an idea i came up with,
Do you have 3-4 friends and want to find the briefcases in LS?
Just first divide the map of LS evenly by 3/4 and then give each section of the map to one of your friends or you and search your section of the map completely, and eventually someone on your team will find a brief location and then you report in and now you know where one brief location is, Which should take only 30minutes-1hour if your team is good. IF you rinse and repeat this your time will eventually get smaller because every time you do this you will know where more brief locations are and if they spawn in that locations, Hey you can just get it.