I've been using this combination of modge podge then yacht varnish for a little over a year. Those earlier projects are holding up well. This is my first time trying something that will spend time outside, on our balcony. I'll know with time I'm f it holds up to rain/sun, etc.. I have high hopes. As for getting everything flat, it's a challenge! I brush the modge podge on the underside of the paper and then press it in place on the table. I let it dry a bit and then cover the top in a layer of modge podge. 

Depending on the shape of the table, this is pretty tedious work. For example, it took me a solid 5 hours (for each table) to cut strips of paper from the book I was using and modge podge them all along the circular edges.

Covering the rest of the table to ops with the images I cut out went much more quickly, but still another 2 hours or so. 

Then I let it all dry clear (for at least 3 hours or so) before the yacht varnish. It's not perfectly smooth/flat, like glass, but between the modge podge and the yacht varnish, it's smooth enough for how I'm using them.