How do you guys drill?

I'm looking to improve on LR overall, and I'm not sure if I should lump together different question types in one drill. If I do this, how many questions should I have in one mixed drill and how do I divide them based on their difficulty range?

Flaw and weaken are two question types I tend to get incorrect, should I drill them separately? If so, how many questions should I add in my drill and how many of each based on their difficulty range?