I have made many, many, many wedding cakes many from scratch and many many from Duncan Hines white cake mix is an excelent product. Try it.
its easy to use and provides ideas on the box for tiered cakes....this is a real time saver and an excelent product an if you are a novice baker you can always get a consistantly good product.
use your time wisely...give the best fillings and frostings.
using a flavored simple syrup is an excelent idea ...for easy I spray it on with a spray bottle.

My favorite icing?
French Buttercream


Amount Measure Ingredient -- Preparation Method
-------- ------------ --------------------------------
2 Cups sugar
2/3 Cup water
6 egg whites
1 Pinch cream of tarter
1 Pinch salt
1 1/4 Pounds Unsalted Butter -- Cut In Pieces
2 Tablespoons instant coffee syrup

To make coffee syrup take a small jar of instant coffee add hot water one teaspoon at a time until crystals are dissolved. Store in refrigerator until needed
dissolve sugar with water in a heavy sauce pan. bring to a boil. boil with out stirring until sugar reaches 248 degrees. while sugar is cooking, beat egg whites with salt and cream of tartar, until eggs are stiff continue beating when sugar reaches 248 pour sugar into egg white mixture in a thin stream as the mixer is running. Continue beating until mixture is room temperature or cool to the touch add butter one piece at a time, beat until light and fluffy add coffee flavoring and beat until well blended. Use at once.