You almost always need to trap problem critters. It is highly unlikely to achieve results strictly by blocking their entry hole. These highly adaptable creatures can be pretty persistent. If you don’t trap certain vermin, they will likely cause more damage in order to get back inside. For example, squirrels often shoot right down the chimney stack if you block them from getting to their nest!
For wildlife like raccoons and squirrels, it is best to positive set a trap over the entry hole. That way they have to go into the trap to get out. Then set a trap nearby to catch whoever isn’t inside the nest. Small rodents like chipmunks, rats and mice can all be removed with snap traps. Legally the only wildlife you can really use toxins against are mice, rats, voles, and moles.