| Moulded plastic parts often have some residue of the mould release agent on them, this is particularly an issue with resin parts. You will need to really thoroughly clean each of the resin parts - I use a bowl of warm water and some abrasive cleaner and a toothbrush at first to scrub the parts. Smaller parts you just need a detergent and warm water - make sure you put the plug in the sink and prior to emptying the bowl - count back in all the parts you've washed and do a sort of dry run to make sure all is there!
Regarding gluing resin parts to styrene - I'd assume superglue would work - but dont have any experience there as I've just built resin kits and styrene kits - without trying to attach resin to styrene.
I've found humbrol enamels to be much harder wearing than acrylics. Especially if you are using an airbrush - acrylics often dry in the air and you end up with a dusty finish which doesn't key well to the surface.
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