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A number of years ago, I bought into a crowdsourced dungeon tiles project, thinking that a dungeon set would be a good thing for TMP to have. When the boxes arrived, I cleverly stacked them up in a location where I would eventually get tired of them getting in my way! So, finally, I am putting them to use.
The dungeon tiles are available painted or unpainted. I purchased an unpainted set.
This set is made of Dwarvenite, a stiff, rubbery material the manufacturer says is similar to PVC. It comes in Dungeon Stone color (i.e., gray). According to the manufacturer, Dwarvenite is an economical material to use for large manufacturing runs. It is also more durable than other materials, such as resin. (It definitely won't break if it falls on the floor. The company says you can chuck them into a bag to take to your game, no problem...)
The three basic pieces are a corner piece, a wall piece, and a floor piece, all supposedly 2" square (actually, just slightly smaller than that).
The reason I'm doing prep work on these pieces is that they all have minor flaws – and when you use the same piece over and over in a dungeon layout, the flaws start to stand out. For example, in the corner piece above, there are several "rocks" at the base of the walls – these are casting flaws. All of these corner pieces in my set have the exact same problems.
Here is the wall piece, and again there are some flaws at the base of the wall, and some bubbles in the gutters between flagstones.
Even the floor piece has two bubbles in the gutters, and one pimple on a flagstone.
(Curiously, only the 'basic' dungeon tiles have these blemishes – I haven't found flaws on the other tiles and parts from the crowdsourced set, which are perhaps made in a different way.)
The tool I find useful in these situations is the ⅛" Marples Blue Chip Chisel from Irwin. This is a quality tool that allows you to put pressure on a narrow area, but be careful – if you slip, you could injure yourself! It works better than a screwdriver, which isn't designed as a punching tool; or a craft knife, which is meant to cut, not push.
To remove a wall "rock," I punch down vertically behind the blemish, then punch horizontally beneath the blemish, and the "rock" slices right off. The "rock" right in the corner takes three punches to remove.
For the blemishes in the gutters between the flagstones, I punch down first on one side, then punch down on the opposite side – this usually causes the blemish to pop out.
Blemishes that pop up out of a flat surface can usually be scraped out, but you need to take care not to gouge the soft surface of the tile. If the blemish is only partly disconnected, gently scrape it from another direction until the rubbery material separates.
Here's a close-up of the corner dungeon tile, once the blemishes have been removed. The piece is now ready for painting.