What cement to use on 1/43rd scale white metal models?

I do everything the Baron suggests. It’s been a while so I haven’t used CA, but epoxy works well.

A question too is prep and priming.

I build white metal kits of figures.  I like to use 2-part epoxy or CA glue.  I'll use the epoxy on joins where there will be greater stress.  I'll pin joins, too, for additional strength, but that's probably not an option for you with this kit.

I would use CA glue

I find that gel CA is better to use than the regular (thin) CA, as it is gap filling, and can be used where gluing surfaces are not perfect fit.  It is a pain on a small metal model working the joining surfaces for that perfect fit.  I personally use Loctite's gel CA.

Hi;

 I did a 1/43 Cobra with wire wheels many , many years ago . It even has opened doors and trunk . Plus positionable front wheels . I used C.A. Medium on all of it . It still looks good today .

It depends on the situation. If the piece is something which carries a lot of weight or bears structural stress, I will solder the assembly rather than relying on an adhesive. However, for most applications (particularly at this scale),  a 5 minute epoxy or standard CA glue works perfectly well to join parts together.