I'm sure there is more than one way to do this job, but as I find myself in a similar situation with a nearly completed Wespe, I intend to follow Bill Plunk's lead on how he tackled this problem. To save me the typing, here's the link;

http://www.bpmodels.net/Model/Album/phpBB2/viewtopic.php?t=48&sid=871c65864ebff37b98e4efd56adc03c2

For me it depends on the vehicle and how much access i have to the inside. I will usually assemble as much as possable and then paint and weather the inside, then work on the outside. I often find the main thing that will get in the way is the gun, so if that can be fitted in later, i will do that after weathering.

Thank you both very much!!

lxion - That build link is perfect.

Bish - Your spot on about the gun, that’s the main issue I have encountered with this Nashorn.

Thank you again! 

I'll certainly be interested to see how you get on with that Nashorn. I have an AFV Club and Dragon kit, so will be keen to see how it goes.

Pretty much the same here, I've only built the Dragon Nashorn and that was decades ago. Assembled the model leaving the gun out, painted everything and then dropped the gun into the fighting compartment. You might want to check to make sure everything fits before you cement it in place though.