Despite the cheap Chinese made PCBs, I still make my own one offs and initial prototypes, only single sided.
What has been working for me is toner transfer with Press-N-Peel film from Jaycar.
Judging by Youtube demonstrations, incomplete tone adhesion is expected, I rarely have this problem now.
The blank PCB must not be warped and edges smoothed, cut it with a hacksaw rather than hand shears.
I clean the copper with a green scouring pad and test the surface by pre-etching for a few seconds looking for
an even matt appearance, no shinny patches which will later selectively delay the final etching.
I rinse off the PCB with rain water and dry it with hot air.
My printer's toner density improves when I reduce the moisture content of whatever is being printed to, with hot air.
I spend some time making certain that the film is thoroughly ironed to the PCB, all of the film area appears well burnished.
I etch in Cupric chloride.
The earlier pre-etching seems to result in less track fattening and a more even final etch.
I set my particular iron to "cotton", 150°C average.
https://www.thegoodguys.com.au/russell-hobbs-rapid-steam-iron-rhc902