Hi,
We've just been through the process with our DD last year. It's not an equal split and no equal marks either.
We did go with a tutor and although I do understand it's financially difficult, there will be stuff your DC will be missing on if you decide to do it yourself as a parent.
Firstly, teaching/practicing anything as a parent-child is a completely different dynamic than teacher-child. Even our tutor had to pay another tutor to tutor their own kids, if that makes sense.
Secondly, the better tutors will also cover strategy and time management. They will figure out how your child learns and how they do tests and suggest an approach that might be best for them.
They can also better explain how to use practice materials. Some of the practice mock test materials, Maths for example, are for 50 minutes each. But the real test is 25 minutes. So you might only want to practice half of it timed and other half next time. But also, some of those tests are done with questions with increasing difficulty and you actually want to split it as all odd questions in 25 minutes, then all even questions in another 25 minutes later. Stuff like this that would not even cross your mind. They also hammer into them how to skip and circle questions they can't answer quickly and come back to them later. And in the last minute, any question that has no answer, just tick anything, you might get lucky. And there's dozens and dozens of tips like that, that they also practice all the time.
If you do decide to do it yourself, do a lot of research into how to cover these additional areas as they can make a huge difference to the outcome.
Sorry, I know that this is perhaps not what you wanted to hear, but perhaps some group tutoring at least every other weak might be financially possible? It could really make a big difference.
Have a look at this charity as well: https://www.aimkent.org.uk/