Need help asap. Never swapped a car before

QLD. I have never sold a car/swapped it before. It works out in both of our favours that I need a Ute for work and he needs a sporty car. I’m doing car + cash difference. I know we both need to fill out the transfer forms and have roadworthy certificates. But how exactly do I do this? Do we both fill the transfer form at the same time? Like I was a little scared like what if he fill mine out and all is done and when it’s my turn to fill his form out he backs out? Idk kinda stupid to even think about since that’s a lot of legal trouble but idk it crossed my mind so it’s been eating me. As for the cash difference it’s probably smarter to do the transfer fully first and then send it via bank transfer right?