Do be careful with the uncured resin you found. I cure all of my prints in cold water, when you expose the resin to UV light to cure, it will heat up as it hardens which WILL distort your print. Whoever sent that to you did so in a hurry and didn't allow for the part to fully cure with UV light. Wash your hands with soap and water and you should be ok.
As per finishing, yes resin will sand much better than PETG and PLA but you will need fine grit sandpaper and a steady hand to get into some of those places. You can also look into resin smoothing, which involves covering the model in a thin resin coat and then curing the thin coat which should even out a lot of the lines, I've seen it done with FDM prints before so give the ole' youtube a look. I am sure you will find what you need.
Good Luck!
