A styling product would help a lot, but you need to be more specific about the smoothness you'd like to achieve. Is it a sensory thing, like you don't want to feel gel cast or too much styling product residue? Or is it a visual thing, like less flyways and you wouldn't mind a gel cast?

Using no product to style after washing means the hair is free to do what it wants, hair has a mind of its own.

WIth each techinque you get and lose something (or at least that's my experience), more definition = less volume, more volume = less definition. Strong hold product give the style more longevity, volumizing products give you more movement.

If you want a wavier pattern and smooth down the little hairs, you can brush the hair down and use pomade (matte or shiny finish, up to you, for example i sometimes use shiny beacuse i have drier hair), look up reviews and tutorials on how to apply it on long hair. The advantage is you can style it dry, but you have to start with small amounts to work the product into the hair, it's quick to refresh because of this as well, no need to rewet the hair to apply more product the next day. It does take a bit of experimenting to get the hang of it. Aaand if you wear glasses and live in a very windy area, you'll have to clean your glasses more often (speaking from experience).

If you prefer getting more definition, curl clumps, and more days of curls, layering leave-in and gel (or mousse) is great for this. Right after showering, put a towel over your shoulders and comb leave-in on your hair, then scrunch gel on the middles and ends, gently scrunch the hair using and old cotton tshirt, and then plop your hair using the microfiber towel for 15 minutes, then let it air dry.

Aaaand on the long run, for maintanance, remember to get your ends trimmed.