I used to weigh the caravan virtually empty other than a gas cylinder, battery, aquaroll, external pump, waste water container mover. Then when I ascertained that weight I knew how much “ personal” gear I could accept before I reached MTPLM. Then everything going into the van was weighed based on a two week holiday in UK. Then I took it to the weighbridge for a check weighing. After that I kept control by using spreadsheets and being aware if anything new or different was used.
Came unstuck once when I was nearly a 25% over MTPLM as weighed at the Brecon weighbridge for a 1000kg MTPLM caravan. As I had not weighed the “empty “van with its basic kit as described above.
For interest anyone know the tolerance on a public weighbridge. I normally used a 5 tonne one at Longleat forestry products site.