Surgery would replace part of the brain with a cybernetic interface that takes a skill chip. The skill chip is a simulated experience and expertise that provides a pawn with skill.
The chips that plug into a cybernetic interface are essentially recordings of someone else's expertise, and so they come in specific levels, such as level-8 cooking or level-10 shooting. Making a chip would involve building the chip and then using a pawn to inscribe their memories. They could also be bought & sold.
Multiple surgeries could replace more of the brain for additional skill slot programming.