I got some beautiful Stockmar block crayons through one of my mommy co-ops. The block shape makes it easier for little hands to grasp (even Zack can use them) and the wide surface is perfect for making rubbings. I would place stencils on his activity table then cover them with butcher paper and tape it down. Sean loves to rub the crayons on the paper and find letters. Sometimes I make words too. He also enjoys slipping letters under the paper and making rubbings of them on his own too.
He realized that rubbings can be made from anything with texture so he has been slipping different things under the paper such as leaves or playdough toys. It has been teaching him to be more aware of textures and the sense of touch.