Yeah... Not my most hated mini by far, but wish I hadn't learned this the hard way.
PAINT THE INTERNAL FACES FIRST!
And then try and make the panel gap as close as possible, so don't mess up when you're cutting the parts out, cough cough, make sure you read the numbers right, cough cough.
The next lot I'm getting will be primed and base coated black on the sprue then any internal faces will be given a top coat. Fetching pain in the arse