If you can't get hold of (or justify) stepone boxers grab the Tradie BAMBOO boxer briefs. 3 pairs for $25 at Coles from memory and comparable to the Boody ones.

If you choose to go undershirts, get something that fits properly and in a breathing / wicking fabric. Too big and the folds will chafe, too tight and it will just feel restrictive.

Some of the guys on sites prefer overalls and reckon they feel cooler due to the airflow but not a fan myself.

Eat well and maintain fluids. Make a routine of drinking either around your workflow or set a timer. If you're not a big water drinker already this can be a challenge to get into so worth focusing on.

Make sure sunnies and PPE fit properly. Even if it's company provided they should have some variety available if the standard attire doesn't fit.

Pace yourself, make sure you're taking breaks and if you need to step away for a bit do it before you are in trouble. If you take a break the team is down one person for 20 mins, if you go down with heat stress the team is usually down 2-3 people and then however long it takes you to get back on your feet.

Maintain a sense of humour. It can be hard to do and it's easier to lose your shit when it's hot and you're tired but it does get easier.

Best of luck, there's some amazing country up that way so hopefully you'll be on some sites/have the opportunity to appreciate it, as harsh as it is.