Well firstly, I have no idea what qualities/attributes are attractive to *these particular* xNFJ's!! I mean, there isn't consistency amongst a given type on who they find attractive and what type of relationship dynamics they want!
There are xNFJ's on this site and irl who are happy with ENTP's, ones who are happy with INFP's, ones with INTP's, ones who are happy with ESFJ's.... and so on. So that needs to be said first.
I can say though that I am involved with an INTJ, and what I think makes our relationship 'easy' is that we both approach the world in the same way - via Ni. There is very little misunderstanding, as we can see each others' pov pretty easily, and also by nature our minds tend to shift and accommodate pretty easily - internal world is a bit more malleable, and we share that, and it's the external that is more rigid. With the latter bit, that makes the relationship 'easy' too - we're both ones who desire closure, and plans, and we therefore both have things we're working towards / it makes planning things together very easy, simply because we both like to plan and have that structure. And I can trust in him, absolutely, that he'll do whatever he says he's going to do. And vice versa. Those are some very high-level things.
Generally, though, there's no 'method' I'd say you should be following in terms of courting.
If you like them, then just show your interest by making plans with them, asking questions, spending time with them, etc. And if they like you, they'll show their interest too. Word of caution with the INFJ... because in some ways she'll approach relationships very similarly to you, it might take a while to know what's going on or whether she's interested. Both INxJ's can be pretty cautious and layered when it comes to that, and if one doesn't take the lead, it could easily just remain in a status of going nowhere (this can be the case with any I/I pairing though, I think).
Just some thoughts. Take with a grain of salt!
