I did see a video on a guy using the acetone method on PLA; although this is most commonly used on ABS and most people say it won't work on PLA, it looks like it worked to a certain extent...he printed in black PLA and when the acetone dried it turned some of the pla a whitish color... so if you're worried about the pla changing colors this wouldn't work....he also didn't vaporize the acetone, he just STRAIGHT dunked it in...I'm not sure if I would go that route but...
Anyway you can find the vid on youtube, probably type in trex pla acetone or skull pla acetone.
I haven't done much research on finishing pla yet, but I know the bondo/sanding/wet sanding should work.
I would like to know if there is a similar method for finishing PLA as well like the acetone for ABS
I use XTC-3D from smooth-on. It's a brush on epoxy and it works well. It only comes with a single 1 oz cup though so buy another 100 for $6 on amazon. It's a 2:1 mix so it helps to have graduated containers for mixing. This sets up super rock hard, which makes over sanding manually practically impossible unlike with Bondo. They each have their strengths and weaknesses but I enjoy using it more than bondo so far.