Jimmy hard top hatch repair

[Sandtrap9072]

So, i am going to attempt to try and fix the crack in the rear hatch of my jimmy. This is my first fiberglass job and may have some questions along the way. Have any of you repaired a cracked hatch like mine? What i am thinking about doing to repair the crack, i will reinforce the inside of the hatch with some fiberglass mat (seems like i can reach it) and then coat the outside of the hatch where the crack is with some fiberglass filler. After that i will sand it down and re-gel coat with a roller to get the texture. Is there anything i should do to prep the crack before i apply the resin? Any input would be greatly appreciated.