Hazardous goods require a DGN (Dangerous Goods Note) for shipping/rail company. If you are carrying flammable it must have the flash point on also.
You also need your information in writing (TREM card) you must have copies in the language of the driver and the language of every country you are transiting.
When transiting Belgium you will need one copy French and one copy in Dutch.
You will need to place hazard warning stickers (diamonds) on trailer for shipping.
You can carry your own or the shipping company will supply them; for a fee.
I’m editing to add. ADR Europe requires that you have two flashing beacons for front and rear of vehicle, and they must work. Take appropriate batteries but do not put in lamp until needed that way they will stay fresh.