When I first tried silicone earplugs I couldn't get on with them. They seemed to create an airtight seal and the resulting pressure of the air trapped in my ear canal was uncomfortable, especially when I was lying on my side and the pillow pushed against my ear/the ear plug.
In the pursuit of a better nights sleep, however, I've ended up using a combination of an in-ear foam earplug and an out-of-ear mold-able silicone earplug. The in-ear foam ear plug is the small version of the
Moldex Contours ear plugs which is quite short in length and barely sticks out of my ear canal so doesn't interfere with the mold-able silicone one. (My ears are probably on the small side, so someone with larger ear canal may need a larger sized foam ear plug.)
I've found following technique helpful in using the silicone ear plugs
-Using fingers, mold the silicone ball into a disk shape, large enough to cover the Incisura, Cavum, Crux Helix and Cymba of your ear
-Use one hand to gentle hold and pull the top of the ear slightly upwards, and the other to gently push the disk, flat side facing the ear, into the shape of the Incisura, Cavum, Crux Helix and Cymba.
The idea is that the silicone will tuck under the Tragus, push/mold into the Cavum and also push/mold/wedge into the Cymba and around the Crux Helix, and this is what will help keep the silicone in place.
If the silicone creates a seal that produces uncomfortable air pressure in the ear canal, pulling down on my ear lobe once or twice and gently wiggling it about a bit, usually releases the pressure, without dislodging the silicone.