Any chances of a picture?
It would be great to see your new plants.
A couple of reactions...
It's really hard to tell the moisture content of the soil from the top layer (that is, the one underneath the top dressing), because that's the layer which dries out first. It takes longer for the soil to dry out at depth, which you can test by putting your finger (or a chopstick or a moisture meter) in a couple of inches. Preferably without causing too much damage to the roots, and not in a repeated way. You can also judge by the weight of the container sometimes. My advice would be to water well (until drops come out the bottom of the container) and then wait and watch until the soil dries out most of the way before watering again. That time interval will be remarkably consistent (no need to repeatedly poke your plants) given consistent light and temperature.
The brown/black spots that appear on some Gasteria leaves are ugly, but I have yet to figure out how to completely avoid them. They seem to come up in springtime, probably in response to the stronger light. They come up even with zero water on the leaves (though it seems wise to avoid that). This time of year a Gasteria will want all the light it can get indoors, but come spring if you find yourself wanting to give it a little outdoor sun, be real careful how fast you ramp it up, and try to avoid more than half a day of sun max.
