The most important resource you need for first aid is not the first aid kit but rather a good practical working knowledge of first aid, its principles and rationale.
Before embarking on a long distance walk I strongly encourage you to get good training in first aid, preferably remote area first aid. The information here simply acts as a refresher and can not be substituted for training, correction and practise.
First aid is the assistance we provide to a sick or injured person until full medical management is available, if required. As first aiders, our role is primarily to prevent more people (including ourselves) from getting injured or sick. First aid is mostly about experience and knowledge not gear.
The third person I found unconscious was laying on their front (the 4th person was in a seat) --, but in all the first aid training and books the casualty was always lying on their back. It is embarrassing how confusing that was for me at the time.
People do not always injure themselves as the book says, so do not simply learn what to do. Understand the principles, and why we do them. Understanding ‘why’ means that we can improvise and deal with unusual situations and priorities them. Many years ago I read ‘The rationale of first aid’ book by St John Ambulance Australia. It was a helpful start in becoming a better first aider in remote areas.
If you have a good understanding of first aid principles, and you have a calm head then it is much easier to improvise and take care of the situation.
It is not just blood and guts, first aid courses are now starting to touch on mental health first aid.
I hope that this area of training will become more common in the future. There are two core streams here; firstly helping people following an emergency, ‘Psychological First Aid’ (similar to crisis counselling), and secondly, ‘Psychosis First Aid’ that helps people experiencing the onset (or increase) of serious mental health issues.
Mental Health first aid may be less ‘exciting’ than dealing with blood or broken bones, but done well it can have an enormous positive impact on the person's life and the outcome of your bushwalk. Although there is no research in the area, I suspect dealing with mental health crises well is likely to save more lives than CPR. I also suspect that training in mental health first aid helps us all cope better when life happens.