You can flambé wine when it's hot enough. We use this method for making a red wine reduction sauce (a slow boil for a while until the gas burner ignites the vapors, then continue to reduce). The majority of the alcohol burns off but there will still be a small amount present once the flame dies. After this point, the alcohol taste will not be clearly identifiable.
A long simmer will also reduce the alcohol (since alcohol is lighter than water) but it will also reduce the liquid content as well. It depends on what you are going for in your final product. For a reduced wine sauce (or other type of reduction), it doesn't really matter which method you use. If you are cooking something within (or around) the wine/alcohol, then a quick flambé can be advantageous to avoid the long simmer time - think flambéd ice cream - you can't reduce that while keeping the ice cream in the same state
Once you pot of wine is at a boil, you can simply take a lighter to the top of the pot. Be careful - depending on the rate of boil and the alcohol content of the wine, it will create different sized flames.
Hope this helps!