Hi @bolly2007,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
You'd have to upload some photos of the cracking so we can offer our best advice. If you need a hand uploading images, please let me know so I can assist.
If it is just hairline cracks, the process may be as simple as widening them using a utility knife, applying some Multi-Purpose Joint Compound to fill the crack flush with the surface, allowing that first layer to dry then applying some mesh tape to bridge over the crack, then applying a second coat of the multipurpose compound to encase the tape, then sanding it smooth, priming and painting.
Generally speaking, this is the process, but I would need to see what you are working with to be sure it will fully solve the issues you are having.
When you've uploaded some photos, I will happily assist further.
Jacob
