I found reading broadly was helpful - finding other people who have similar experiences of gender as you and who have written about it can really be helpful for discovering yourself.

For transmasc experiences:

• We Both Laughed in Pleasure by Lou Sullivan
• Becoming a Visible Man by Jamison Green
• Welcome to St. Hell a graphic memoir by Lewis Hancox
• Gender Queer another graphic memoir by Maia Kobabe

Personally I found "experimentation" worthless as a trans person, e.g. when I was in denial and I would try to crossdress to see how I felt, it always made me feel worse. Makeup made me feel worse. I misinterpreted this as evidence I didn't find those things gender-affirming. That said, it's a common suggestion and you could try it out and see if it helps.

You could try one of those apps that gender swaps your face - how that makes you feel can be some indication.

You can always just try HRT - that's a valid way to try to figure out how you feel.

Obviously a good idea is to find a gender-informed therapist (ideally someone who has lots of experience with other trans patients) to help you walk through how you feel.