Apply liberal (lotso) amounts of ATF (Automatic Transmission Fluid) on the drivetrain (chain and derailleur). No need to disassemble nor remove any part. I prefer to use syringe to apply ATF to minimize mess. One big drop on each roller and plates, big drop on each pulley axle and also big drop on each derailleur joints.
Be sure to put newspapers under the bike and between the drivetrain and the rear wheel. Back pedal slow to distribute, wait an hour, backpedal fast to fling away excess ATF and finally wipe off excess ATF with rug from the chain and derailleurs. It's the best method if you lack time and resources for an OCD-level drivetrain job!
ATF will degrease, clean, and lube the chain all at the same time!
Use Dexron III or higher ATF