Mikey,
Can i urge you to reconsider your plans? Gluing the deck after painting might leave a bit of a seam in need of filling, especially on the larger scaled uboats...would be a waste of the time you spent painting it...
For what it's worth, i generally assemble the hull and deck completely and paint the separate pieces by masking (after the filling part ofcourse).
Instead i leave off the conning tower untill it is painted. Some dryfitting, adjusting and then supergluing it on the deck and you can start the weathering This way you can paint all separate pieces and minimalise the seams showing up later.
Again, this is just constructive advice taken from my own experience. Your model, your decision ofcourse
Richard