Ahoy Blackwind,
I don't think there is any difference between satin finish and semigloss. I've seen the terms used interchangeably. There may be a subtle difference that I don't know of but It escapes my understanding.
I haven't tried this myself but am going to give it a shot. Yesterday evening I was reading an article from the May 2001 Fine Scale Modeler by Bill Pettyjohn describing his painting/weathering technique. During one of the steps, he applies common household furniture varnish thinned with mineral spirits. I am almost certain you could find a household varnish with a satin finish at a hardware or paint store. Mr. Pettyhohn is not the first person I've read of who uses common household varnish as part of his finishing technique. I think its worth investigating.
When I was building rubber powered, stick and tissue, flying scale models, I would tint the finish without adding much weight by adding a small amount of floquil color to clear nitrate dope. Worked very well. I mention this to assure you that there are ways to tint clear coats and suggest that a variation of this technique could be used with household varnish.
Hope this gives you something to chew on.
Tom
Hope this helps.
Tom