Agree with the prior posts. The better the brandy quality, the less warming is needed. Cheap brandy should be warmed by being poured into coffee. Slightly better brandy warmed by rinsing the glass with hot water (or hot air drying in a dishwasher). Sufficiently good brandy should not even have that, no heat at all (not even the hand), but this is for the Paradis and up category when it matters (old brandies become fragile and are more like perfume than brandy, so there is a big difference in how the aromatics behave).