Whats it made form mate? looks like you dont have many curves there? all those angles are going to be a pita to bondo and sand to get the right shape. The best way would have been to make it to the right shape to begin with? nice curves where needed then fill any areas that need it and sand smooth then primer and paint or gelcoat ?.Just trying to save you some hard work,you might think youve saved time making the shape as you have but in my opinion youve added to the task as i dont think you will be able to get it to shape the way you suggest without a lot of filler and hard work sorry .Good luck with it though,seems like everyones making moulds from these plans lateley.
Mart