Here are some tips:
Use a small brush nozzle to clean the tiny holes in the basket more thoroughly. A brush-equipped rinse nozzle works best.
Don’t worry about minor blockages. The basket holes are extremely small, and any blockage will be naturally cleared by the pressure from the next shot, without affecting extraction.
If you’re concerned, place a piece of coffee filter paper at the bottom of the basket before dosing for extra peace of mind.