Best options/ideas for waterproofing prints

I am just wondering what are some of the best/easiest options people have used for making prints watertight? In this case, I do mean post-processing - I have played with and tested different printing techniques, from thick nozzle vase spiral prints, to lots of perimeters and messing with where seams are placed, as well as different materials. But I am curious as to what are the most convenient things to apply to prints for waterproofing. My goal here is to make simple spiral vase prints for plants (PLA, PETG and what I actually wanna try now - Prusament PVB). So, not super watertight (not holding water, just temporarily moist soil). Extra points for ease of application (is there something like spray epoxy?) and potentially being non-toxic (not doing edible plants or anything, but that's always a plus with children in the house). Thanks for the help!