Most flash photography videos that I am watching use a model, telling her to turn left, chin up, etc. But I don't have a family or friend around to practice on, and because one of my main goals is to get into portrait, wedding, people photography, I want to practice on something as close to the shape and size of a human. What do you suggest I use?
Tethered selfies are easy to setup, or you could give a try to an "Hair Styling Head" even though that could feel creepy.
My solution to this was to do party photography at a local bar to try new techniques and light modifiers. Everything had to be quite portable, but as everything i used was DIY i could deal with it and not be afraid of having it damaged.
Getting at a party with crazy DIY photography stuffs is a good way to get the attention of potential models.
I ended up doing ~130 studio photo shootings over 2 years this way, and ~400 nights at the bar shooting. It helps being a student in this situation.
A few people use a polystyrene head on a light stand or table, but I've not been able to find one where I am so I use a cable release and shoot myself until I have something approaching usable then call a friend in for the minimum amount of time I can.
This takes longer than shooting a head on a stick, but works just as well, a chair helps you keep the positioning consistent and tethering is a huge help.
Have a look if there are any local studios, groups, clubs, etc that get together to shoot models.
A studio close to where I used to live used to run regular group shoots. Not only was it great for practising and shooting different models in different setups, but you could also see how other photographers interact with a model, and it was great for socialising too.