Is brushing your tongue with a toothbrush recommended? Do damage?

Yes. Gently, when you brush your teeth. Just enough to "wipe" the surface a few times. Will Not do damage. Can help freshen your breath.
Tongue scraper. There are OTC tongue scrapers in pharmacies and supermarkets made specifically for that purpose. They work better than toothbrushes but I sometimes use a toothbrush myself. No damage with either as long as you don't overdo it. Once per day is more than enough.