Befriending an outdoor kitten?

My family have discovered a stray kitten thats been living near our house, come to find out that he/she has been taking shelter in and under my dad’s car. Last week I was only able to catch glimpse of them sitting on the porch or loafing in the driveway, but just today I was able to watch them eat and get close enough without them feeling like they need to climb back in the car and hide.

We’re trying to befriend them to the point where they feel comfortable interacting with people, we can’t keep them because of our dog (He’s not aggressive, but he is shy/scared of smaller dogs so who knows how he’ll act around a kitty). But we plan on homing them with my brother and his girlfriend, kind of like a foster situation.

Are there any tips to get them more comfortable? Also some tips on sheltering him better incase it rains?