i didn't apply for or get into baulko so i can't speak for that. also i wrote edutest ages ago in yr 9 for yr10 entry and i was a competitive candidate (got a first round interview and then i decided to drop out of the waitlist so idk what realistically would have happened but i was 1st or 2nd reserve)
given that info, i used a site called notesedu for online exams which helped when i did hast, and i noticed it helped for edutest too. ifor me i didn't find the questions in edutest themself that hard it is only the time limit that was hard. also any questions that i did find hard/unusual i took screenshots of it and wrote like a detailed solution/strategy that i could use to approach the question. i don't have access to these screenshots but yeah you guys should do this when you prepare.
for writing i practiced using yr6 selective prompts (the prompt i got on exam day was like a phot of a dark brick tunnel and we had to write an imaginative, so yeah kind of similar to selective). aim to finish with time to spare so you can check over your work and things like that. based on the rank i got and the thing i remember writing, they usually care more about the actual content of your writing as opposed to the concept/plot. so you could write a story with a meh premise but a really good usage of literary techniques etc. which will get you far
i can't lie i find verbal reasoning really easy and it was def one of my strengths, not that i did any special prep for it, i just used notesedu and spammed exams.
for abstract reasoning its almost always about pattern recognition. there are tons and tons of other exams from all over the world that uses like some version of abstract reasoning and for that reason there are tons of videos and resources on yt etc. that teach you strategies to approach the question. when i did selective there was a similar section called general ability, and so you can use old selective resources in relation to that, which can potentially help. spam question papers and form strategies on how to approach question
for maths again i just spammed questions. this section is especially time restricted and the question are not that hard. spam questions and when you get better and better try restricting your time limit
reading comprehension requires the ability to skim effectively and read quickly. if you're a reader this usually comes easy to you, but if you aren't its really worth practicing imo. also i really recommend that if you get a text that you have to use for multiple questions, read the question first. somethimes you dont have to read the whole thing properly as long as you get the gist. the question will also indicate what you need to focus on if you do need to read it and this will make the process quicker.
hope that helps. ulitmately it does come down to spamming practise exams. always do them in timed conditions, dont get used to doing them normally bc when you consistently work under timed conditions you will be more aware of what is consuming your time in an exam and do better next time.
i used notesedu but you should def ask someone that did the test more recently for more up to date advice