Here lately my buttercream is not crusting. I always make it in advance like a week and freeze it.  So I always have a bout 5-7 5lb buckets on hand. 

Recipe:

2sticks butter

2cups crisco

2lb bag of powder sugar

2 teaspoon flavoring.

Only mix it for a few minutes... when I was whipping it for 15 -20 minutes I was told I was putting to much air in it. 

I read somewhere that frosting a cake cold makes it crust well I tried that and it didnt work out. Than I tried just letting it sit for a few minutes but it ends up being a mess.  

I really need help with the cake market changing and more people are starting to dislike fondant on cakes I have to learn how to "BUTTERCREAM"  a cake smooth as fondant. 

Did your recipe used to crust?  Or has it never crusted?  Crusting is a fat to sugar ratio.  Refrigerating it won't make it crust nor will putting it on a frozen cake.  The crusting recipe I use has 2 cups fat to 2 pounds sugar.  Yours has twice the fat.  You might want to try a different recipe, one that says it crusts.

AYeah you have to much fat and not enough sugar in your recipe for it to crust. If you want a butter/shortening buttercream try starting out with a cup of each to 2 pounds of powdered sugar and some flavorings it should crust with that ratio to ratio amount.

So 1 cup butter 1 cup shortening 2 pounds powered sugar Flavorings

What makes icing crust is a lower fat content compared to the amount of sugar.  The recipe you mention is almost exactly the one I posted as "2 of everything Icing" (except there is less flavoring).  It will not crust.  But as another poster mentioned if you reduce the 'fat' it will.  

..........Only mix it for a few minutes... when I was whipping it for 15 -20 minutes I was told I was putting to much air in it..........

This is BUNK!  If you read my posted recipe it is mixed for at least 10 minutes for a super smooth, easy to use icing.  It is better to use a narrow, deep bowl so the beaters of the mixer are completely burried, but even that is not imparritive(sp?) :)  

Do check out my post: http://cakecentral.com/a/2-icing  Read the whole post and try it.  I think you will really like it.