Carrot question from newbie madredhead

I have got a bit carried away with planting things from seed.  My carrots are lovely but only tiny and very fragile.  How do I move them and separate with out damaging them? What size should they be? ??

The question was asked in the Welcome thread, here

http://chat.allotment-garden.org/index.php?topic=114591.msg1316913#msg1316913

If you have grown them in pots or trays, get a bucket of water and swish the clump of seedlings in the water. This should seperate them enough to allow you to transplant them without too much damage.

I found you could grow them in root trainers or deep paper pots but it's a real faff unless you only want to grow a few.

I've never had much success with transplanted carrots they always end up forking, if there's a knack to this I'd love to know. I always plant direct and thin out but I am sure I'd have more success if I could start them off in the greenhouse

Stupid question but what is the advantage of sowing carrots in pots or trays?  The dreaded carrot fly?  I always sow directly into the ground and thin out as they grow and, unlike a lot of things up this way, I have always managed a good crop of carrots.  I protect against fly by building a structure around them, high enough so the flies can't get in