Well, first remove the slide and then remove the back plastic part (slide end cap no.28) of the slide.
You will need to push back the striker assembly (no.23) inside (white plastic part) to remove the cap cause it make a pressure on the slide end.
Then the striker pin disassemble completely.
Clean the interior of the slide and the striker parts with a good cleaner such as CLP Power blast. You may use some Q-Tips to help.
Let the CLP work out en then just clean with a regular solvent and reassemble.
Here is a diagram to help...