Wolfgang,
I NEVER cover the seedling pots except to protect from cold. If they don't get strong light they will become etiolated and extended. Those types of seedlings are very difficult to transplant. Also they NEED light to do photosynthesis. They accumulate malate at night but fix it in sugars during the day.
You do want to keep them wet for quite a while. After transplanting, I water them FREQUENTLY until I see new growth. I use a transplanting type liquid fertilizer when transplanting and then once/ week through the season. You are more likely to lose them for LACK of water than too much. I slow down watering and fertilizer and water in September so they will harden off before winter.
As Lynn can tell you, the growth I get on seedlings is quite phenomenal. I have plants with 5-6" rosettes one year from seed with numerous increase.
Hope that helps!
Kevin
