"Use a Post-It Note's sticky backing to get a grip on the SIM card's smooth surface"

Good suggestion. Alternatively..........use a pencil eraser!

I found removing the SIM/SD card with my fingertip a little difficult – not enough friction. So I used a 'rubber' (in US English it's called a pencil eraser or just simply, an eraser.

Simple, cheap (zero) and effective! :)

Cheers.

John