I was talking to my mom and she took a cake decorating class a long time ago and she remembered they used Crisco to practice different decorating techniques and then were able to just wipe it away and put it back into their bag to keep practicing. I am new to the whole cake decorating world and need to practice, a lot, but don't want to spend a ton of money on frosting. What are some good, cheap ways to practice these great decorating ideas?

to practice , I just make up a batch of royal icing, one eggwhite and about 250 g of icing sugar mix.
I start with the eggwhite add a pinch of cream of tartar and about half a fingernail of meringue powder and whisk in the sugar a teaspoon at a time , until you have got an icing that will hold it's peak but is not too stiff.

any left in the bowl , cover with some plastic wrap toching the top of the icing and it will keep for up to a week in the fridge , just give it a good beat up before you use it again.

I wouldn't use straight crisco.

Personally I think when practicing you should use something like you would be using for the actual cake.

http://www.wilton.com/recipe/Buttercream-Icing

In the Wilton classes we use the above recipe, but with 1 cup of crisco and no butter. You can also replace the milk for water, and if you are just practicing you can leave the flavoring out.

The recipe as started is for stiff buttercream, which is used for roses. For medium buttercream which is what you use for stars, borders and about 3/4ths of the decorations on the cake, use 3 tbls of water instead of the two. For writing, leaves and icing the cake you would use thin icing, which would be 4 tbls of water for the whole recipe.

This icing can easily be used to practice piping, scraped up, tossed back in the bag and used again and again and again.