I didn't tutor for the 11+ and got kids into super selectives and independent schools in London but effectively I was the tutor. I went over maths concepts, did Olympiad problems with them, analysed texts, taught them how to read poetry and fiction. Started with 15 mins a day and built it up. Just 1:1 time with me every single day including holidays and weekends. The aim of all this was obviously the 11+ but I wanted to make sure that in the maths and sciences they had super strong fundamentals and they could apply these concepts, and that in the humanities they also had a really strong base-so for me it wasn't just about the 11+ and the exams. I approached it as a 'these will help them in school' and if they have solid concepts then we can introduce exam technique.
So yes it's possible without tutoring but there are two factors. My children don't mind learning with me, and are not resistant. In fact they both quite enjoy that 1:1 time with me. Two, it is a lot of time to invest, and alongside my full time job I had to make sure I was fully prepared to support them and that I wouldn't resent the time it takes. But for me I enjoy teaching my children, and learning alongside them.
I agree with the person who said I could personalise the learning to my children as well. They learn very differently and have very different interests and also doing it this way put less pressure on them- because I made it about them doing their best and learning more, rather than here is a set of exams you need to crack. I'm also conscious that this approach is not feasible for everyone!
Finally, I continue to offer support in secondary school. DH and I sit down with the kids at the weekends and go over topics taught (humanities and sciences), make sure they keep up language revision in half term and holidays, I taught him how to make notes and revise, and generally I keep track of his progress, and step in when I think he needs help.