Can you walk me through the steps please? How exactly do I do this through coinb.in?
It's not hard to make unsigned raw transactions from Coinb.in. Anyway, I'll walk you through check the image below.
Under output ignore the 2nd address if you want to send the whole BTC from your old wallet(which is your friend's rooted phone) to the new wallet.
And take note of the transaction fee make sure to pay enough fee because I have a bad experience before that I accidentally paid a large fee without checking it.
I forgot to mention the inputs tab but as you can see on the image it's all of your combined amount of BTC(Total amount of your BTC)
Then submit it after you set them properly and you will see something like this
That's your raw/hex unsigned transaction now paste it to this tool
https://coinb.in/#verify to check if everything is fine. If all are fine now you can transfer the raw/hex to your rooted phone through OTG or any way to transfer without using the internet.
Once you transfer you can signed the transaction and transfer it back to your online machine and broadcast it here
https://coinb.in/#broadcastI hope that you can follow...