Do not forget this old homemade standby and one that is easy to concoct: A mixture of liquid model cement and (poly)styrene. Once combined, the liquid cement melts the styrene into a paste-like consistency which can be applied with the aid of a syringe.

I'd wager that it is one of the more stable weld replicating procedures since the "welds" become permanent and a part of the vehicle once they completely dry. This is excellent for a model that will be handled a lot.

My 2 cents...