It depends on the kinda mistakes you are committing.
If you are committing lot of conceptual errors then i would suggest
CR Powerscore Bible for CR and Manhattan SC ,Kaplan for SC besides i would advise you to go through every SC problems in
OG-11 ,but dont forget to go through the explanations given by them. Go through the explanation of every problem you solve. Even if you have got the question right.
If there you are committing many silly mistakes then it shows lack of practice. Solve 1000 CR and 1000 SC .
You can start solving Brutal SCs once you gain confidence.
HTH
Good luck