When you have some sticky residue on silicone you can soak the silicone in some warm water with dawn dish soap.
The Dawn Dish Soap should help get rid of the sticky residue so that it washes off the silicone really easily.
You can also use some baking soda and pour it on the silicone and then scrub the sticky residue off.
If that still doesn't work good enough then you can use some purple power degreaser in some warm water which should help get rid of the sticky residue from the silicone.
You may need to soak the silicone in hot water for a few hours to help get rid of the residue but it should wipe off eventually.