<p>I'm new to 3D printing. I've made some projects before just fine, but this project is giving me problems.</p>

<p>I 3D printed a trumpet mouthpiece, and the printer made supports inside the mouthpiece funnel. I can easily remove the exterior supports, but I don't know how to get to the supports inside. Does anyone know how I would do that?</p>

<p><a href="https://i.stack.imgur.com/U6ys5.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/U6ys5.jpg" alt="Here&#39;s one image."></a>
<a href="https://i.stack.imgur.com/DJ9KP.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DJ9KP.jpg" alt="Here&#39;s another."></a></p>

<p><a href="https://www.thingiverse.com/thing:1539908" rel="nofollow noreferrer">Here is the link to the model</a>
<a href="https://i.stack.imgur.com/8R11d.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8R11d.jpg" alt="enter image description here"></a></p>

Based on the photo provided, there's a strong possibility that you can print that model without internal supports. The angle of the walls falls within the limits of just about any FDM/FFF printer. An exception to this would be if you had a structure internal to the cone of the mouth piece which needed support.
ERROR: I neglected to note that your print is created "laying down" rather than vertically. This certainly complicates the printing/support problem. I typically print cylinders without internal support, although it does result in a small amount of droopies within the cylinder. Those are easily cleared away as required and much more easily than a full support forest.
Is it impractical for you to consider to cut the model in half, print both segments, remove the supports more easily, then glue them together?