First, You recognized your mistake and you are actively fixing it. That is more than lots of people do so don't beat yourself up or get discouraged.
I can attest that positive reinforcement is effective. I have been extremely lucky with my bird Mushka in that she has progressed very quickly and I have been able to see the difference on a daily basis. It takes many birds months or more to really get results but it really does work.
Mushka was a rescue bird but she was well taken care of. At first she was very cage aggressive, and very aggressive with most people and animals no matter where she was. She gave several very bad bites, and severely injured a BnG macaw twice her size. The BnG nearly lost his tongue and a toe. I got lucky and for some reason Mushka liked me from the first but she wouldn't step up or let me take her out of her cage or any number of things. I had been researching quite a bit and I had owned smaller birds so I had CONFIDENCE.
That is a big thing, don't let your mistake make you timid, your conure will gain confidence only when you have it. These little guys are very empathetic and your attitude makes a huge difference. Make every interaction with your bird positive as much as possible. Let your bird make the first move. When you work with him remain positive and happy, find out a good treat that motivates your bird and and let him come to get it from you while you talk to them in a positive way. If you need to, give it to them through the cage bars for a while. Sit close to them where they have access to you but don't approach them, have a treat or a favorite toy and just act positive and happy. When they show interest offer a treat. Read a book with your bird close so you are just a constant part of the scenery but no threat.
I let Mushka make the first move from the start. I would offer a treat, but she would have to approach me to get it. I didn't scratch her head unless she came to me and asked for it. As we progressed after she came to me I would ask her to step up and would let her come to my hand. If she moved off I wouldn't chase, just wait while I talked to her. That never worked with her, the first time she stepped up was when we were playing with a toy and she just stepped up. After doing this for a month visiting her for an hour a day I went in to pick her up. They came out with leather gloves and a perch to get her from her cage and I just reached in and let her step up and got her out of the cage. All because I was confidant, always let Mushka do what she was comfortable with, and made every experience I had with her positive.
Since coming home I have had others repeat the same process with great success. She is a much more personable bird with everyone, and will step up for others and even let others scratch her head after she gets to know them. We still have a way to go, she still won't let anyone other than me take her out of her cage in the morning, she will still nip others if they get to pushy but it isn't her first reaction anymore and she doesn't draw blood any more. In a few months Mushka went from overly an aggressive bird that others were afraid to handle without gloves to a very well adjusted bird who is now curious about new people.
Target training may be good as well, especially if they are afraid of your hands. Lots of good videos and posts about target training online, and I have seen people work with skittish birds and get them used to hands by gradually "choking up" on the stick end eventually eliminating it all together. So there are several options out there to see what works well for you and your bird.
Obviously Mushka's situation was different from your bird, but the methods remain the same. Be confidant not forceful, give your bird the time they need, and make every experience end in a positive. I am not a bird expert but I am proud of my relationship with Mushka and what it took to get here. Once you take the time and put in the effort you will know that your bird's relationship with you is something to be proud of. Birds don't immediately naturally trust people and when you earn it you feel great and know it was worth the effort.