My favorite method is to use ganache because it is easy to make and falls beautifully on bundt cakes. Allow the cake to cool fully so the ganache doesn’t melt off. Place the cake on a cooling rack, then place the cooling rack over a cookie sheet. Pour a thick layer of ganache onto the top of the cake, allowing it to fall down both sides. After you’ve gone around the whole cake, go back while it is still wet and add more ganache in any spots that are bare or look odd. Lastly, pick up the cooling rack and tap it gently, but firmly, on the cookie sheet. This will help the ganache fall evenly and smoothly on the cake. Allow to set for about an hour.