How do I cover bulbs in silicone?

You don't, the bulb might explode. How is 25 watts too bright? Use a 15 watt bulb or equivalent in LED. Here is a comparison chart.

https://www.bulbamerica.com/pages/wattage-lumens-brightness.html

Do not put anything on the bulbs. Silicone can melt, smoke, and start on fire. And as Naomie says the bulb can explode due to confined heat build up.

Tape parts of your buld, and then spray with heat paint. That is paint that was made for heated places. Then take off your tape.

We had a low wattage bulb in a lamp that was too bright for my hubby in the bedroom. He covered the top of the shad with a light cloth to limit some of the light. Never cover the bulb.