Yes. As with any prep, the old paint must be given a "tooth" for the new paint to grab. This is done by sanding or painting it with a special primer that will give it a "tooth". Either way it must be...
You will have no problem painting satin over top of flat paint. Just remember to use the appropriate paint that will stick to the old coating. If the old coating is latex (water based) you can go...
Yes, Eggshell and Satin are very similar. Though i would recommend scuffing the walls with a sanding block or sandpaper to help with adhesion . Also current and new colors will make a difference, you...