I figured out a technique to help guys get some solid practice flirting through messaging apps. It is very amoral, however I am not tied down by morality. Remember,

Don't hate the player, hate the game All is fair in love and war.

Use Grindr. I am bi and was actively improving my seduction skills before I ever used grindr. I figured this out recently though. I do occasionally hook up with guys from grindr but I've found the app hugely beneficial to learn to seduce someone through messaging if you don't have many women to practice with.

Get on grindr. There will be some guys sending you dick pics and offering their buttholes to you but you can ignore all that. Start messaging guys with the intention of figuring out how to effectively make the other person respond in a way that you want. Go about it just as you would a woman. You need to immediately get their attention, slowly real them in, put them at ease. Be patient. You have no intention of getting laid by this person so feel free to try out all your lines, words, ideas and you can figure out your best method of message seduction. You'll have exactly the same conversations that you'll have with women.

Men and women are different but many principles of seduction apply to both. Though different things stimulate a man and a woman, both genders can be played in almost the same way. Being bi doesn't hurt, I mean you need to be able to make a person horny, but even if you're uncomfortable talking dirty with guys, it's a good way to gain experience if you don't have plenty of women to practice on.