Types can be not as you think. IR can be good or bad - it's not known.
Duals understand each other instinctively. Mainly do what other one wants by common doing of what they think as appropriate. They need external help the least. For good relations what they need is to be in a compassion to other one and to care to make him feel better, - from both sides.

"Dualization" is the supporting of weak regions of other one and geting alike for yourself. Through valued regions, mainly.
There is nothing special to know for concrete types besides basic theory.

As an advice for good IR I'd say that they have good possibilities to improve support in relations, emotional state of both. You invest efforts and this brings a profit, gratitude and return support - such happens in good IR. As values are same, so both think about what makes the life better similarly (in related to Jung types).

With duals is a problem of initial difference in views according to strong functions. People are partly different in how to act in the life, from what point they see it. Both have weaknesses where other one is strong, so opinions and behavior of other one may look there naive and kiddy. Own weak regions are adopted to be underesteemated in importance. You feel a sympathy and general interest, but to respect a dual and his opinions takes some time, to understand better his part of truth. In result both may change understanding of some things, to sum own and dual's view - to get wider and wiser understanding. This happens not in a moment, so needs a time to be patient as with kids, to teach each other about other part of truth. By words and seeing what other one does, how he thinks and perceives the life.

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With concrete human, in case you think it's good IR, - talk directly about what you think and want, what you feel. Ask about what you doubt and want to know more. With good IR acting openly gives more chance to improve, than to harm relations.