yep what Bill says,,
was your Iwata a full size gun, or a detail size,, I have one of the Iwata detail guns,, it atomizes wonderfully,, but its not suitable for clears or single stage materials,, its awesome for base coat colors ( in a two stage system, base clear), then I use my Sata minijet for clear which is bar none the best most reliable gun I have ever sprayed with,, but like you say,, filling it is interesting even with a stand,, I made my own stand that wraps around the cup,, and has sides to capture the grip, its bullet proof now too,,
I started with Sharpe guns,, then got a DeVilbuss JGA ,, it was a very versitile gun ,,