ACan I use the store bought buttercream and do the viva technique?
Generally, no. Store bought icing doesn't crust properly and that's necessary to use the paper towel method.
ADo you have a recipe that you use, that tastes good? Thank you!
I have used the Wilton Extra Special Buttercream recipe for years. When I first learned the recipe--from a Wilton class book--it didn't state that it needed refrigeration. It contains lots of fat & sugar, both great preservatives when found in large quantities. I don't refrigerate cakes with it on. I tell people they should eat the cake, if it room temp in no more than 3 days, or they can refrigerate it for up to a week. I freeze leftovers all the time.
If you need it to crust heavily, you can add another 1/2 to 1 cup of powdered sugar.