Tip time, take it or leave it
I don't have years of experience but I have done a LOT of brass.
Etching primer does not perform on brass and car primer is too thick.
I use this chemical for all flux removal and cleaning.
I use exclusively Tamiya FINE primer for plastic & metal in grey or white.
Tamiya also dries fast and I top coat this in less than an hour.
For the crane to cabin fixing I've used a brass split pin and once formed around a same size steel rod I have soldered the split.
Once set up on the model at the right height and angle I've CA'd the pin to crane.
The instructions show brass nail through the top of the crane arm then bent to carry the pulley hanger.
I found this impossible and used brass wire instead and soldered a nut on top then filed to shape