getting different "clear" finishes?

Correct.

It can be done with different gloss paints or -- perhaps more easily -- through the use of semi-gloss, satin or matte clear coats after painting. Depending on the size of the area to be covered, those clear coats can be brushed on, as well as masked and sprayed.

You can vary the sheen somewhat when airbrushing by how dry you apply the paint.  You can make gloss paint look semi-gloss by increasing air pressure and putting down a very thin, dry coat.  You can use flat paint and use lower pressure and put down a very wet coat.

It is great if you can buy gloss, semi-gloss and flat paint in the color you want, but unfortunately you do not have that choice for most colors.  Black is about the only color that is readily available in all three sheens.

Semi-matt clearcoats are rare in model paints, but clear polyurethane is available in all three sheens. It is possible to airbrush polyurethane- thin well.  However, do a test to check compatibility of polyurethane with the paints you are using.

I don't know what paints you're using but Tamiya sells a flat base that you can use with their bottled acrylic clear to achieve whatever level of satin or matte that you need. You can also use it in their gloss colors. It's basically a paste that you add to gloss paint to flatten the finish. Would take a little experimenting to get what you want but it works. 

It may work with other brands of paint as well but you would have to test that. I have used it in AK's Real Colors clears and Testors GlossCote with no problems. Also be aware that if you do try it, the more you add the more likely you are to actually see it over dark colors.

Or, you could use a matte clear and add gloss of the same brand to get the sheen you want.

so in relation to this thread:

Turns out in my bag of (yet unused) tricks I have a clear product from Alclad2 labeled "light sheen"...am I to assume use of this is similar to semi-gloss? 

MRP Paint also has different clear coats.  I think they have 4 different types that cover the range from gloss to flat, and in-between.  So far, I have tried their Matt Clear paint and it did a better job of knocking the gloss completely out after I decaled and weathered my F-16 than my Testors Dullcote did.

Not sure about the Alclad Light Sheen, but you can try shooting it on a painted spoon and see if you like the effect.  As I have seen recently, whether or not you get the effect you like can be very brand-dependent, and its highly subjective from one modeler to another.  I used to be completely satisfied with the Testors clear paints.  Lately not so much.