Yes indeed, the freehand router makes work a lot easier. All of that uncolored example piece (and more work since then) was done with the router, and all done with the exact same wire pattern on the router. Since then that practice block has been made to look like similarly all the way around.
I don't think that I am going to need the sanding disc / sanding drum on a rotary tool that the guide I borrowed from mentions using. (I also hate the mess it creates.) I definitely
won't need a knife; I experimented cutting through EPS foam and pink foam and the sculpting tool does the job so much faster it's ridiculous.
I don't know whether or not melted EPS can leech through a good sealant, so I can't recommend these tools for anyone trying to create a vivarium prop with animals living near it in the tank. But for all other purposes, hot wire tools are a godsend.
As far as colouring Drylok goes:
It took 3 gallons & 1 quart of Drylok experimenting, involving various acrylics and concrete dyes, to finally arrive at a color as near to the base colour I want the foam to be painted with as can reasonably be made. (Without turning the whole mixture into acrylic paint.)
I did the mixing next to my previous terrarium, with its 6500K lights, as those are most similar to the quality of lights that are going to be used in the terrarium containing this model. There is a noticeable difference in the shade or tone of colored Drylok between being under this light and being under a warm, 3100K light.