It depends on the doubt and what it's about.
I get periods where I doubt the efficacy of practice, and it saps my confidence. This kind of doubt and worry is like a magician: it uses sleight of hand to get you to look away while it works in secret. In this case, the doubt is really in the doubt itself, the worry really is in the worry itself. The pain of doubt comes exactly from the momentum built up in doubting: pursuing possibilities, leaving the present moment, chasing "what if..." scenarios, the friction caused by constant restlessness. It may make you feel helpless as well, stuck in indecision. The Buddha compared doubt to striking out into a desert with no map and no provisions. You wander around for a while, then maybe some bandits kill you after a time. I've come to know that place rather well
Doubt is convincing because it makes you feel like you're being reasonable, doing your due diligence, trying to "get it right".
This is where "doubting, doubting" can help to step out of the proliferation of doubt on doubt. It's not to sweep things under the rug, but to stop pouring gas on the fire.
But not even just that: probe into the doubt. What does it feel like in the body, for instance how does it affect the breath? Can you pinpoint the first link in this particular chain of doubt? What seems to set it in motion? Where does it go when you do not doubt?
See its impermanence, its contingency on other things to arise, and the suffering it causes. Really study your doubt while it's there. Be like a physician carefully and skillfully inquiring into a patient's symptoms to find the best course of treatment.
What ultimately helped me out of a months-long morass of doubt was the Buddha's summary: Suffering I teach, and the way out of suffering.
Don't fly after whatever doubt tells you to, usually some metaphysical truth or something better "someday". Instead, take your suffering for what it is, no matter its cause, and see what you can do to relieve it.
And don't forget: when doubt is not there, notice that too.
Best of luck, from one chronic doubter to the next