Just got my second car after 6 years with my first one. So far I used to go top up my tyre pressure as soon as I saw that tyres started to show visual signs of needing it. Apparently that's a bad idea.
An article suggest to "push the thumb into the side of the tyre". But 99% of what I find say a tool is required. I feel this is overkill and unnecessary in most cases.
What easy, tool-free method is used by lots of people throughout the world?