I'm very confused about the teachings of the Holy Spirit as our guide and teacher.
That seems you do not know the Holy Spirit. Then spend more time in meditating on the Word of God. Do in-depth study of The Holy Bible/Scriptures. And pray asking the Lord for the Holy Spirit. Luke 11:13- So if you who are evil know how to give good gifts to your children, how much more will your Father in heaven give the Holy Spirit to those who ask.
how do you discern between what the Holy Spirit reveals to you and a product of our mind?
If you delight in the Lord, love Him with all your heart, mind, and soul, and if you are following and living in accordance with the Word of God, then your mind aligns with the Holy Spirit. Then you will hear one voice, your mind and Holy Spirit saying the same thing. If there's anything in your lifestyle that is not in accordance with the Word of God, then your mind and the Holy Spirit are in conflict in that issue. You discern what is the Holy Spirit saying by comparing it with the truth that is in the Bible, so you know what is good and acceptable to the Lord.
For example if I wake up with the revelation that God is a huge flying pineapple, how am I to know that this knowledge didn't come from the Holy Spirit?
You know that is not from the Holy Spirit because that knowledge does not align with the truth in the Word of God that He gave us.
Unless the we can directly sense what is from the Holy Spirit or not, how can He really teach us?
If you abide in Christ, sincerely following Him, then don't worry about sensing or not sensing. What you need will be given to you when you need it. Luke 12:11-12 Now when they bring you to the synagogues and magistrates and authorities, do not worry about how or what you should answer, or what you should say. For the Holy Spirit will teach you in that very hour what you ought to say. So just keep going, make your plans, and commit your plans to God, He will determine your steps. Proverbs 16:9.
What also confuses me is how the Holy Spirit can remind us of scriptures, but again it's confusing because it could be either from the mind or the Holy Spirit!
Be Christ-minded. Set your mind on the things above that are of Spirit and on the Kingdom of God, be transformed by the renewal of your mind. When we accept Christ, you become a new creation, you are born again in your spirit and you have a new mind, that is united and one with Christ, so can put on Christ, not your old self anymore but He lives in you. God has written His law in our mind, so it will remind you the scriptures. There's nothing to be confused about it. Let your mind rest in Christ.