Any suggestions to cure headlight misting on a 300TDI. Dried itout with a hairdryer, still came back. Somebody suggested putting silica gel in, but would that work, worried that interior temperature from bulb might ignite it.

Any help appreciated.

Cilica gel has high absorption of moisture, and from any where so it would soon be a floating mess inside your head lamp, you may have have a faulty seal between glass and reflector u could try and reseal but normally its a new headlamp required.

I had the same problem last week. Took two goes with a hair dryer to get it really dry. Give it about 15 / 20 minutes of hot air. Takes a bit longer to get the moisture out of the perimeter as the air stops getting right in to the seams.
If you get it really dry you should be ok.
IF it comes back, remove the light from the truck and put a smear of plumbers silicone around the edge.
Tool it with your index finger covered in spit the spit stops the silicone sticking to your finger..... But you knew that already.( allow it to harden for a full day , or even two is better.
You can apply a fair bit of heat to the lamp as they get hot when the lights are on but don't overdo it and wreck your plastic backing. Best of luck. It worked for me.
Regards Nick.

Yes, tried both of these, even got the glass off and resealed it with silicone, but problem still exists. Should there be some sort of vent to allow the moisture out (?), I notice that later models have vents.

Regards