I swear by what used to be called "killed spirits" or Zinc Chloride, still available under the "Baker's Fluid" brand name. It will make solder unite with almost anything except aluminium but is quite acidic - it must immediately be washed off any steel/ferrous metal but there is no gummy/waxy hard residue to scrub off.
The reinforcements added on one front and one side.
Question to everyone: as can be seen on the first photo (look at the prototype) the couplers, include the coupler-box, are very short on this kind of cars. I've got a pair of Kadee bettondorf trucks include the couplers but the couplers come too far outside the truck. Anyone has a suggestion for trucks or couplers?
Done with the main parts. Details come later. The trucks are just for the picture's.
I think I've also found a solution for the coupler length. I can shorten the coupler-box a little and put them a bit further on the trucks. I have to do some work on the trucks for that either, but that's ok.