Glad to help BT. Using spray cans is always a difficult business on models, as there just isn't enough control. The gloss varnish is probably OK, but matt, due its nature is more tricky. Try using the following for matt, as it can be applied by paint brush, without leaving brush marks. Experiment first though.
Use Johnson's Klear, and pour enough for the job into a small container or jar. Add a little Tamiya acrylic Flat Base, and stir well. Try it on a piece of scrap, and wait for it to dry, which doesn't take long. If it is not matt enough, add a little more Flat Base and repeat. If too much Flat Base is added, it will dry with either a milky appearance, or with chalky looking 'dust' present. The latter is far too much Flat Base, the former just a little too much. To correct, add a little more Klear.
Not a very precise 'recipe', but it works, just needs a bit of trial and error.
Brush onto the model, ensuring the brush is not overloaded, and lay it off properly. (brush out until more required), ensuring the brush strokes go one way only. Leave to dry. If any 'pools' appear, or drips form on trailing edges or other sharp areas, use the edge of a piece of tissue to soak up.
Once dry, as Klear is self-levelling, it should look uniform and free of brush marks, and will give a good matt appearance. The sheen can be varied up to semi matt or semi gloss by the addition of more Klear.