How can I put numbers on a cement block ( it’s already dry ) ?
Hello would a sharpie and paint work? Many crafteres use the oil based markers for stencil outlines and fill the center in with paint like indoor-outdoor acrylics.
If it's outside I'd use masonry paint to be sure it didn't weather off over time :)
You might even be able to use a stencil and some spray paint.
Could you do a mosaic.
Or paint it with masonry paint.
They also sell brick clips at hardware stores that allows you to hang things on bricks without making holes.