All of my cats are feral born and I have seen them display a range of behaviors from overtly friendly to all humans after an initial wariness period that usual lasts less than an hour, to so anti-human that a couple will not come out from hiding if any other human is in the house. I had a house sitter tell me that in the entire week he was taking care of them, he only actually saw 2 of the 5.

Here's my tip for you, which has worked very well with my most timid cats:

When you need to walk close to or by them, do not make eye contact. Just ignore them. After a time, they learn that just because you may walk by them doesn't mean you are going to grab them or anything and they learn to just hold their ground. This is very useful if you don't like steppnig on little feet and tails, or if you object to tripping over them, which I sure do!

The slow blinking tip is very good advise. And playing on the bed while you are lying down is also very good. It puts your face and the kittens' faces at the same level which is more comfortable for them, trust wise.