How to wipe phone completely? For customs in airport, so it has to be extra clean

I'm moving to Australia and I'm worried about getting pulled to the side and getting a phone check and I do have something to hide lol nothing serious but things I'd rather they don't see/ask about.

I read some people do factory reset but I read that's not enough as the police is able to look for data that was deleted.

I am moving in a month so I'm thinking of I wipe everything now and just install some apps …

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