Other then playing both hands, which works fine but bluffing yourself in edge battles might be difficult, not sure how solo can work here…
I have been doing this a lot lately. My local game store closes relatively early (8:00 pm), and with family responsibilities, I can't really leave the house before then to go play a card game. I've had some very fun solo me vs. myself games. The tension of the edge battle is removed, and you can't really get practice with that bluffing aspect of the game, but I tend to look at it in a few ways:
1) I at least get a game in since I'm dying to play it every night.
2) It's a fun exercise in seeing how certain decks will match up against each other or see if a deck has enough resources, too many resources, etc.
3) It's great tactical practice because it forces you to think from both players' perspectives and you can start to see how to maneuver an opponent into a sort of checkmate.
Finding an opponent is obviously superior, but I'm finding that these solo games are pretty fun too.