I use a really nice Windows program (which is free) called WinCompose. It adds what’s called a “compose” key (default is the right Alt key) to the keyboard, and everything else then becomes really intuitive.
Eg, to type é you press the compose key, followed by apostrophe, followed by e. To type ç you press the compose key followed by comma followed by c. For ê it’s compose, ^, e. For ã it’s compose, ~, a. For à it’s compose, ` (which is normally in the top left corner of the keyboard), then a.
There are thousands more combinations, for all sorts of languages, but those are the ones I mostly use. They’re quite intuitive. Comma for a cedilla, apostrophe for an acute accent, etc etc.