Looking good but...if I may add something:
1, The periscope covers look too thick now. Perhaps you should thin them out a little.
2, Why go to the bother of making the periscope glass from putty? Make them from clear plastic stock instead, much easier and more realistic.
3, What are the holes on the front of the bulkhead in the last photo of the front of the machine? If this is supposed to be the flaws in the concrete add on then they are too big. Cover it with putty and get some green scouring pad and before the putty dries, dab it with the scourer to make SMALL imperfections.
4 re. painting see this:
Painting guide