My sims have started the R&D skill as Young Adults straight from CAS. It only took a few hours to reach level 3 using the research machine at the BriteChester library. You'll gain R&D skill for any topic but Research Methodology gives the most. Level 6 took a bit longer than level 3. Most sims will spend many hours doing homework, presentations, and term papers, so anything that makes them faster will save time over the long run.
You can also Practice Debate at the mirror or on a debate podium, read skill books, or take part in debates.
