Duce

As said before, Simply getting a dcent spray to represent the main colour of his army, then doing minor details like the guns, eyes, belts, shoulder trims, eagles would be sufficient enough... the spray alone would make them better since they'd all be the same colour and provides 2 things. 1- making the job of painting so many models much quicker and easier 2- much cheaper than getting someone to paint them.

Hey, Firstly props for going all out and getting a huge army, i'd love to do the same but painting is a put off for me. A suggestion may be to get an undercoat spray the colour of the chapter your doing. then use boltgun for bits on the guns / vehicles. Red for the eyes then 2-3 more colours for details. this will cut down on the painting time by a ton. mainly because you undercoat everything say blue, then touch up each marine with boltgun bits, eyes and minor details. then ocne you've completed all that you can come back and do more details as you feel fit. Your army is so big that that level of painting is enough in my opinion to make it wow worthy. Who cares about the cost, your having fun, unlike drink you've something to show for it ;)