I'm in the middle of scratchbuilding a very large diorama project, and before I move on to the walls, ceiling, and electrical, I'm working on some foundation, but mainly the flooring. I know there are many different ways to go about producing what I was after, but I am a very literal person, so I went for the literal interpretation: shaping polymer clay (Sculpey III & SuperSculpey Original), cutting, baking, sanding, and painting about 600+ tiles all the while doing actual tilework and grouting. I figured with a job like this, that using actual, real grout (or something similar) was going to be waaaay to difficult and messy, so I figured I would go a different route with caulk and glues. Well, I was partially correct. I used a combination of Elmer's "Glue-All", Elmer's standard white, DAP Dyanflex 320 (window/door/trim caulk), Custom Building Products' "SimpleFix" Ceramic Tile & Fixture Caulk, and to make sure it's white, I added a small splash of Behr Premium Plus Ultra ultra pure white (one of the 8oz sample canisters you can get from a hardware store's paint section for cheap). I mixed everything together inside and dispensed from Elmer's Glue-all bottle because the applicator tip is conveniently sized

What I did was cut a measured section of blue insulation foam, measured and marked a grid, glued a single layer of cheesecloth over the grid (I thought this would give me optimal adhesion for the tiles), and the individually gluing every tile in place . My issue was that after the first application of the glue-caulk mixture, the mixtures was a little too loose, so as it was drying, it seeped into all of the cracks and crevices under and around the tiles. On one hand, this was a boon because now my tiles will have a solid base, on the other hand, it became a messy nightmare because after everything dried, the caulk mixture looked sunken and pockmarked, which forced me into a second and third application of the mixture (and one final, fourth touch-up). To simulate the look/aesthetic of real grout, I lightly sprinkled some local gray-white sand I sterilized (baked at 500°F for one hour) while the mixture was in place and still wet. Enclosed are the results to that first section.1/6 Scale Tile Work & "Grout" (WIP)-tile1-jpg1/6 Scale Tile Work & "Grout" (WIP)-tile2-jpg

Have any of you folks ever attempted anything like this? Is there a better mixture I could use to fill in the gaps of the tiles as a "grout?" The mixture I am using doesn't fully mix, unfortunately, and you'll experience times where it is dispensing at the right viscosity, and other times when it's a thick bead of caulk spooging out....
I could really use some suggestions for a better filler material to use as the "grout" so I only have to do one application (plus a touch-up if needed, is completely fine).