Where can I find and how can I type special Irish letters, such as vowels with fada, on my keyboard? Are there recommended keyboard layouts or tools for typing these characters easily?

To easily type special Irish characters like vowels with a fada (á, é, í, ó, ú), you can use online tools such as Creative Fabrica’s text generator. It lets you enter accented Irish letters, choose a font style, and copy the result for use in your projects—perfect if your keyboard doesn’t support direct input of these characters.

If you are using Windows, you can install Microsoft PowerToys from the Microsoft Store. One of the tools is called Quick Accent. Once you get Quick Accent set up and get used to using it, adding fáda ₇ ṡéimhiú to your letters is a breeze.

I use a keyboard layout called "Extremtastatur" (a newer version is called "Europatastatur").
It is made for a German keyboard, only, I think.

(Á, é, í, ó, ú are easy to write with the normal German keyboard. But other Irish variants as ḃ, ċ, ḋ, ḟ, ġ, ṁ, ṗ, ṡ, ẛ, ṫ, ɼ, ⁊ or almost all diacritics of other languages as ł, ğ, ț, č or German variants as ſ, ẞ can be found easily there.)