The technique that worked for Me is the big dog little dog technique. I bet you can find it on Google, but if you can't, I'll be happy to explain it.

Once you've got a technique that works for you, the next step is to sing in the shower! Every day, for months! You'll sound like a demoness in no time!

There are YouTube videos for free, yeah

There's "how to talk like a girl good", and https://www.youtube.com/playlist?list=PLYJkVI7LLpknvBww07jnsxbz-_Lkynsry this one (trans voice lessons), and I used those for free and now having a passing fem voice

I can highly reccomend The Voice Book for Trans and Non-Binary People by Matthew Mills & Gillie Stoneham. I'm sure our friend Anna has it in her Archive if you don't want a physical copy

Trans voice lessons on YouTube

One quick voice training trick/tip to get you started.

Simply take your tongue, and if able, place it on the roof of your mouth. Far enough to feel your muscles in the back of your neck tense up but also be careful to not choke yourself or anything. These are the muscles you need to keep tense. Now that you can feel which ones to target, simply drop your tongue back to a normal position while also keeping those neck muscles tense and then attempt to speak normally.

If done correctly, you'll find that you'll talk softer. This trick demonstrates an example of resonance. It can be quick to pickup and use, but difficult to sustain. But that's where practice comes in. ;-)

Also don't forget to drink water. It helps a lot during practice.

Here, also, is my favorite voice training video that covers this trick in the "positioning" section: https://youtu.be/4AesESPasZw?is=KRJ1UpbHlQzAnj8m

Seattle Voice Labs, they have a discord where they do public lessons and have many amazing resources:

https://discord.gg/xgkjtUA4M

I'm currently doing voice training through Undead Voice and am nearly finished. It's pricey (I jumped on a discount), but worth it for the right type of person who values live interaction and immediate feedback, since you have to do voice check-ins every unit with the instructor to move on the subsequent parts of the course.

I needed the structured approach Undead Voice provided and wouldn't be where I'm at now without it, after trying Transvoicelessons on YouTube and not making any progress, but on the other hand, I'm really not a video call person and the Zoom Fatigue is real.

I think if you have a trans friend to practice with IRL, that's ideal and you can save a bunch of money by just watching YouTube tutorials.

In addition to the resources mentioned, Seattle Voice Labs has excellent lessons (but also pricey) buuut they have some really good youtube videos as well!