Your first consideration should always be fire-safety. Think about where the heat is being applied, in addition to where the hot flakes of paint will go. Many a decorator has come unstuck, for example, when burning off the soffits of a house. Flames don’t know where they’re supposed to go, so if there is a way through the surface to the dry old timbers in the attic or a hidden bird’s nest, they will soon burn through, and fire spreads very quickly. Unless you can see where the heat is going, don’t risk it. Always have a suitable means of extinguishing a fire to hand and remove soft furnishings from the area.
Also consider the age of the paint and whether it is likely to be lead based. Lead is toxic and heating the paint will produce lead-laden fumes. Simple lead testing kits are available. Always guard against inhaling toxic fumes - ensure adequate ventilation and wear a suitably protective mask.
Hot air gun or torch
Heat can be applied either with a hot air gun or a gas torch. The former is a lot easier to use if you have no experience with a gas torch. Gas torches are a lot faster but more difficult to control and HOTTER.
Heat the surface of the paint by playing the gun back and forth to distribute the heat evenly. As the paint gets hot it will blister. It is at this point that it is easiest to remove it. Do not allow it to get any hotter as it will ignite and smoulder. Excess heat will also scorch the surface. This can bleed through new paint, or leave unsightly marks if the wood is to be varnished.
Small scorch marks can be prevented from bleeding through by applying a coat of knotting.