Latex and acrylic (both water-based paints) do come in a semi-gloss finish.
You can purchase a semi-gloss enamel in both water and oil-based varieties.
There are flat paints that are made to go over semigloss paint. Many inexpensive flat paints will peel almost immediately when laid over semigloss. The most common solution is to roughen the surface of the semigloss (sandpaper, sandblasting, steel wool, or trisodium phosphate). The actual requirement is to remove alkyds which migrate to the surface of some semigloss and gloss paints. The alkyds make it impossible for latex or acrylic to bond to the surface underneath. You also have to remove buildup of dirt, mildew, etc. Most primers are suitable for recoating semigloss. Read the label. A layer of primer followed by your flat paint is generally the best solution if the surface is relatively clean. Benjamin Moore Fresh Start interior / exterior acrylic primer is one example of a good primer for this application.
Doesn't the amount of varnish in the paint make the difference?
Yes you can, just clean the old stain with steel wool or fine sandpaper before you do.
Yes, however, if it is an oil-based clear you'll see an amber color to the tint. Water-based clears tend to be crystal clear and do not affect the underlying color.
Primer for the 1st coat. Have it tinted with color you plan to paint to make application of paint go faster. You may get away with only painting one coat if lucky!
If it is flat paint, you can apply the texture without any additional preparation. If it is a gloss or semigloss, you will need to rough up the surface with sandpaper first.
Yes, significantly. Try mixing different amount of each until you create the sheen you were looking for
If you mix a flat and semi-gloss 1:1 you should end up with a paint in the eggshell range. Mix the same paints 1:3 and you should end up with a satin. Experiment with small amounts to get the desired gloss.
Yes you can
oil base primer ( kilz or zinzer), ask the paint guy at the local ace hardware, sheerwin Williams or lowes . let it dry good
yes.