Cant thin my MM enamels right! splatter/watery

Well, you may have noticed my recent post, and I didnt start a new one to fill up the forums with duplicate posts, its jsut that now I have a  completely different problem.  Ive got an aztek a270, and It comes with an open toppen container and two glass jar type containers.  I tried the galss jar containers and no paint reached the tip, but the opened topped one worked.  I don't know why, but it did.  Anyways, Im using Model Master Enamels, and thinning it with ThinX-100% odorless mineral spirits paint thinner, and it either comes out splattery with blobs and lines, or watery and in little drops, and it never comes out consistantly, I get like 2 seconds of spraying, and then it stops, and I ahve to readjust stuff and turn up/down the pressure before it works again, and then it starts over.  The thing thats most annoying, is that I also have some Model Master pre-thinned (airbrush ready) enamel paint, and it works perfectly, no blobs, no drops, so Im pretty sure its the thinning that Im doing wrong, since that works so well.  What should my ratio be?  Its white enamel paint if it matters.  Thanks.