Train, car, bus connections are with the local town on the Polish side, Terespol.
By car
By car
See Belarus. There are six control lines of various sorts at the crossing. Allow something like 2 hours to get through them all.
If you are already in Terespol and need to cross over to Brest, you can walk over to the border crossing and "hitchhike" across with one of the cars that is already towards front of the line. They might be happy to take you across as they can "assign" some goods as belonging to you for the purposes of customs. Just go along with the arrangement. Alternatively, they might ask for a modest payment of $5USD or so.