First time I am going to used this. I need to know if to fill the cake with this as it is or should i mix it in buttercream icing. The reason I am asking its because I dont know if its too soft for the cake to stay outside.

Make a good stiff damn and use the filling as is; thin layer.

I mix it with bc all the time. I find the sleeved fillings to be too slippery otherwise.

I agree with Leah strawberry filling is to slippery. One of my caketastrophe was a strawberry glaze filling. I like the strawberries and cream filling on CC. Strawberries n Cream Mousse
Ingredients

1 large pkg of Instant Vanilla Jello Pudding
1 Pint of Heavy Whipping Cream
2-3 tablespoons of Strawberry Jello Gelatin Powder (you can add more or less depending on how much strawberry taste you want!)

Instructions

Mix Heavy whipping cream on med-high. Slowly add all of the contents of the Instant Vanilla pudding and strawberry gelatin powder to whipping cream until it reaches a thick mousse and all of the gelatin and pudding mix is dissolved. Make sure the jello is dissolved before whipping. If you want a filling that doesn't need refrigeration use Bettercreme or Frostin Pride in place of the whipping cream.