Genesis 1:27  So God created man in his own image, in the image of God he created him; male and female he created them.

Call them to repent and put their trust in Jeus Christ.

You wrote, you "want to support them however I can. I’m not interested in ‘talking them out of it’ or anything,"

If you have no concern for their rebellion to God, you are not a Christian. If you promote and tell them their confusion is righteous before God, you are being most unloving.

If you are a friend, just be there to be a shoulder to lean on when they need it.

This confusion is caused by demonic activity.

Removing fiery darts by faith:

Eph 6:16 In all circumstances take up the shield of faith, with which you can extinguish all the fiery darts of the evil one;

1) Ask permission - "May I pray for you?" If they grant you permission then (optional) you may also ask "Is there anything in particular you would like me to pray for?"

2) Pray: "Lord, would you show me what fiery darts you want me to deal with, anything you would like me to bring out?" Or customize the prayer to fit their request of what they specifically want prayed for. The more general the prayer the better.

3) Remain silent for up to 10 seconds while observing the other person.

4) When you see something in or upon the other person share what you see and explain it to them. Do not let anything you see startle or frighten you. Demonic attachments can take many different forms and you have power and authority over them ALL in the name of Yeshua ("Jesus").

Luk 10:19 Behold, I have given you authority to tread on serpents and scorpions, and over all the power of the enemy, and nothing shall hurt you.

5) Ask their permission to remove it and carefully do so. If there is anything embedded in them carefully pull it out in a way that it will do no more damage. For example, do not pull an arrow out the way it cam in, but push it through so the barb at the tip does not enter again. Crabs may have their claws dug into a person - gently pull out each claw before removing the crab.

6) After removing it, hand it to Yeshua ("Jesus") to be disposed of. "I give this to you Yeshua." and then move it away from the other person and let go of it.

7) Pray for healing and recovery. "In the name of Yeshua ("Jesus") I command healing and complete restoration of any damage done. Amen."

Your friend had the courage to come out of the closet as trans, it’s time for you to come out of the confessional (or pew, pick one) as a Christian, to your friend.  Offer to pray for him/her, and if she/he doesn’t want that do it in private anyway.  

When the friend definitively decides on his/her gender.  Use the preferred pronouns, but don’t keep apologising if you use the wrong ones.  

Find the names of reliable counsellors who specialize in such disorders, and give the names to them.

Gently break it to the guy who wants to become a girl that he'll never get pregnant no matter how much "she" tries.

Christianity imposing a bunch of gender norms on the masses is the cause for this whole mess in the first place. 

How can you even begin to help them, when you are not walking the True Christian Walk? i say you are not because they don't even know you are a Christian. Are you ashamed of Christ, and don't want them to know, or are you a Christian only behind closed doors, either way, NOT a True Christian.

If you want to help them, then get right with God first.

You can help by listening.

You don't have to 'do' anything else.

~

I’m a Christian.  My friends ARE having gender dysphoria. How should I help?

edit:  There's no reason to be offended by correct grammar.