The shop vac is to remove remaining water. Not necessary if you're switching buckets.
Even lifting the lid won't be easy if you scrog because the screen will be in the way. I think I would avoid the screen and just trim them short. I'm really impressed with the idea of using a tent. Make sure you place a fan close to knock the plants around. This is necessary because if you don't gets the plants to bounce a little, the strems won't strengthen and they plants will fall over, believe it or not. Ideally your space isn't any hotter than 75F.
Dynagro fert is also good. It's a one part for veg, one for flower. One teaspoon per gallon in hyrdro. Use good quality air pump. People use air stones, but know that they start to crumble and bit sit in the bucket. It's probably not a problem, though. If done right, they will grow like mad. You'll have to do daily maintenance on them however, checking the ppm levels. Don't try to fight pH too much as it will drift. Maybe do some reading from a book on hydro will help.
Slime that shows up in the water is algae and the result of a light leak, so make sure no light gets to the water. Some hydroguard will help. don't add nutrients like extra calcium and magnesium unless you're sure you have to. People keep doing that but your fert should have that stuff already. Perhaps use boiled water that has cooled, to prevent pathogens. Distilled water you buy might be good too. Putting buckets on platforms that have wheels will make for easier pulling, pushing.