I have a crappy looking la confidential that I had in a 1.5 gallon pot of MG organic choice GARDENING SOIL, NOT potting mix, which is not only bad because its MG, but its not even potting mix. I ended up transplanting her from that crap, into a netpot 3 days ago.
What I did was use a 5 gallon bucket of 70 degree water. as close to room temp as I could. I dumped the plant out in my hand how you would normally do it for transplant, took a quick look at the roots and whatnot and dunked it in the bucket and GENTLY swished it around till all the dirt was off. Took me about ten minutes total. Mind you this was a clone I had put in, not a seed and it was not planted in rockwool, it was a jiffy cube. This seems like the worst possible thing to do right?
End result after all the washing off of dirt was a 14 inch root system due to growing in the pot for about a month.
Now just to give an Idea of how shitty she was doing, I was looking at 2 inches of growth in height for the past month. FAIL SOIL.
I took the girl and plopped her gently into a netpot and covered with hydroton.
Oddly enough she didnt even droop from stress or anything, Shes already an inch taller than she was 3 days back.
I only just started doing dwc myself so I'm learning too. I'm using a 3 gallon bucket with a drip system and airstone.
I really wouldnt recommend transplanting from soil to hydro unless it was absolutely neccessary. I also think that I might have gotten lucky this time as I heard LA confidential can be a pretty forgiving strain.
I've also never done autflowering plants before so I definitley don't know how they would react to it.
To be honest I made a thread exactly about this 3 or 4 days back because I was in the same boat as you.
As for the waterline/mesh level thing I've had people tell me to keep it about an inch or so. Roots will go anywhere they can to find moisture and nutrients and I'm not sure, but it might help them grow more.