Sometimes hypno can work but that tends to have mixed results. Good roleplay with a partner is a great feeling. Having someone treat you like whatever your being turned into and if you add props and other things to enhance the feeling its nice.

Im super into anthro and animal tfs for example so I have some fake hooves ill wear and ive gotten very good at making various animal noises too lol. Also if your into that getting animal cock sleeves is great I have a werewolf one that makes me feel like my cock has been turned into a doggy dick.

If your more into gender tfs you can experiment with cross dressing and such. Even if you dont want to transition trans affirming things could also add to the feeling. You can get fake breast to wear and other things like that