I disagree it’s difficult to cover a small area which has been prepared before, and this is from a man who isn’t particularly handy, and ceramic coated my own car. The difference tends to be longevity, as professionals often use high quality versions, which are baked on. Home use versions tend to max out at 2 years.
The ceramic liquid, applicator, and topper is £50. I rate cquk 3.0 for ease of use and longevity.
You can also use a ceramic topper such as reload, which goes on like a spray wax, and contains sio2 ceramic, but longevity is 4m or less.
However, to be honest, I will not ceramic coat a whole car again. It limits the cleaning chemicals I can use to wash it, and it took 2 full days of prep. I’ll be paying a professional next time or sticking with regular waxes.