After a few paint and wash layers:

The egg carton was starting to get weak from all the moisture, though, so it was time to seal it (with my own special sealing mix, mostly white school glue with a bit of water and some Minwax semi-gloss waterbased sealer); I soaked it pretty well for the first seal (wasn't stingy, went through alot of glue), let that dry overnight, and then just gave it a decent over-cover for the second seal:

It is pretty sturdy right now (I mixed heavy on the glue so it would be) because I will have to scrub on it fairly heartily with a wet rag while I'm applying grout, so I need it to be able to stand up to that pretty well. I also painted in fairly dark colors because my experience with my Spring Fling bricks was that the color gets washed out a fair amount under the grouting (at least for the way that I have been applying it) so it needs to be striking...

I didn't take a picture of the SF bricks before, but here is one of them after grouting:

The color pre-grout was a very strong brick-red so you can see how much it has been toned down by the grout. I think that I will touch up the chimney stones after grouting, even, so as to not lose too much of that dark contrast...