I was about to remove/replace the trigger spring in my CZ 452 UltraLux, but realized that I hadn't found or bought a derlin bench block. I am very finicky about potential blemishes in my firearms.
Went to the cheap toy section of a local drug store and bought a single plastic "egg" containing "Silly Putty," a fascinating toy from my youth. As far as I know, the stuff is non-toxic, hypoallergenic and adheres to very few materials, especially metallic items.
Simple: pancake the putty into a shape to place beneath the (trigger) assembly, place it on a piece of paper (you'll NEVER get this stuff out of any cloth/mat you place it on - it will adhere to cloth/felt fibers when hammered) and hand-press the mechanism into the putty until it is slightly depressed. You now have a custom mold. Hammer away.
Neat things: the hammered pin will penetrate the putty and stick (no more pin-searching), the putty distributes the force of blow to the entire mechanism and "rebounds" to continue providing support, it's reusable forever, it will accommodate ANY firearm and ANY mechanism, it leaves no residue (even in fine cracks) and IT IS CHEAP AND AVAILABLE EVERYWHERE.
Next: Some use for Sen Sen as a solvent!