Not much choice other than what you mentioned, at least that I'm aware of.
The colored die spacers for me are the quickest and cheapest option. What I do is to use a die hardener around the margin to help prevent die chipping, fit the emax (LiSi, trans zi etc) check occlusion etc all the way up to glazing, then I put the colored spacer on. I apply it just slightly shy of the margin edge, as that will help enough in getting that ging 1/3 color for final shading. I then let my account know that everything was confirmed (margins and fit) before I put the spacer on so they don't need to worry about margin integrity if I happened to get spacer right on the margin.
If you want, just use the colored spacer on your solid cast for checking contacts or with a 2nd die pour up. I'm just starting to do printed models, so I'm not sure how the colored spacers work on that type of "plastic".