Get a length of welding rod, heavy fencing wire of straighten out a coathanger & fashion a stand;
Fold it about 45dergees in at the centre, this will form your base, at about 15>20cm back from the bend, fold two vertical uprights from the remainder, retain about 20cm for the uprights & bend the remainder parallel to the base & chop these at about 15cm (in elevation it would look like a C & in plan it would look like an M)
You now have 2 15cm rods that are about 20cm above & paralell to the deck - the rods can be easily slid into the nacelle's of a twin to hold it,or into front/rear or side mounted intakes or exhausts. The whole arrangement can the be bent / twisted to get the model to the precise angle you require. Whatever side you do first doesn't require the use of this, but if it is sitting in when you complete your first side, you can just turn the whole model around & sit it down on the stand to continue painting.
I have used this method from a 1/72 BAE Hawk, up to a 1/72 XB-70 & it worked fine on both.