Dog travelling abroad

I’ll be sending my dog from the UK to Aus next year and it’s really stressing me out.

He’s a rescue so it’s taken a lot to get him to a calm-ish happy place but we can’t leave him here.

I was just wondering if anyone has done this and did any pre training? Anything that helped them to relax and be calm around new people?

Or any tips? I don’t know, any advice would be good I suppose.

Thank you