Another thing I thought about....
I often use water based Varathane floor finish for *utility pieces, not fine furniture. I almost always get air bubbles you describe. I remedy the bubbles by applying a good coat of finish, then wipe my brush relatively dry with a paper towel, then slowly brush back (1 or 2 strokes) over the application. The dryer brush seems to pop the bubbles while the finish is still wet. I immediately repeat this process, if need be, and almost all the bubbles are removed; very little, if any, bubbles remain. The first dry-brushing collects some of the bubbles on the bristles, hence, wiping the brush again, to remove those bubbles, then swiping a few more gentle brush strokes.
I like Bob's spray bottle recommendation, also. I always spray finishes when convenient. I've never used a manual spray bottle, though, so I need to try it. Any miscues should be able to be cleaned up, "fixed", with a small brush and gentle brushing of drips and such, similar to brushing small drips when spraying with air guns or aerosol/rattle cans. If you opt for a manual spray bottle, do some practice sprayings if you're not familiar with them.
*I recall having this bubble issue when finishing this rocker, made from salvaged cypress lumber. The whole of the wood surfaces were not completely smooth (I like the rustic look and "texture" of unrefined wood), so those irregular wood surfaces contributed to creating the bubbles. The dry brush, paper towel technique resolved the problem, as with other pieces I've done.https://www.flickr.com/photos/43836144@ ... otostream/https://www.flickr.com/photos/43836144@ ... otostream/https://www.flickr.com/photos/43836144@ ... otostream/