Sorry old chap, bit late replying. The easiest way is to paint the doors whilst on the sprue, then remove, fit into the wells, and hold them in place (inside) with a small ball of Blue Tac or Plasticine. Apply the decals, let them set, the apply the clear coat. Once dry, carefully cut through the joints (around the doors) with a SHARP scalpel. Remove the doors, ready for placement later. You might get a small bit of 'chipping' on the edges of the decals, but this can be touched-in later.
It's a pain, but it works ok - but I'd love to get hold of the p***k who thought up the wondeful idea of positioning the serial numbers in such a stupid place! I bet the painters of the real aircraft had an even bigger problem, unless they put the kite on jacks, with the gear retracted.