I used fire paste for preheating my Optimus stove and it barely did that in the worst weather.If you're looking for something along those lines, IMO a small container of white gas would do you better.

For major rain/wet wood I always carry at least one road flare. If the situation is so bad that you need really serious fire starting help, a road flare is it. It will burn , once lit, in almost any weather. Keep it in a vacuum sealed bag and it will be ready when you need it.