My flows are kind of terrible.
I've practiced flowing rounds on youtube (which tend to be nice and neat) but as soon as I'm in round and I'm working out arguments, writing cx questions, figuring our rhetoric, and gathering evidence they get messy fast. My writing gets bigger, the arguments flow weirdly (bad placement which results in confusing arrows), and in my speech I do this weird hopping from argument to argument thing (and hope I hit all of their arguments) as opposed to going down my flow systematically.
1. You're probably writing too much. My in-round flows when I'm debating typically consist of one or two words at most for each argument tag--with bullets for different warrants/things that I want to mention. Your brain is an awesome thing: you can remember flashbacks from ten years ago with the mention of a single word. It can definitely be trained to keep track of an argument for eight minutes with one or two word tags to help.
Hopefully you'll get to the point where you're writing virtually nothing in your opponents column except the things which you'll mention in your response. This will give you time to preflow everything in your speech before they sit down. You can train your brain to respond to one-word triggers for things that have already happened, but you can't do that for phrases/rhetoric/strategies that have a nifty way of escaping you right as you go up to speak.
Make sure when you're practicing you're practicing as though you're in a debate round--not as though you'll be quizzed on it by a professor or trying to get as much detail as possible because that's going to make you feel like you have to do that in the round. Just try to predict what the opposite team will say if you're watching a youtube round.
2. You might be listening too slow and thus feel rushed. Focus on prediction when you're listening. You shouldn't have to wait to the end of a sentence or argument to know exactly where the other team is going with their argument. I'd typically spend the first five-ten seconds of an argument listening and the rest writing out responses/looking for evidence while I'm sort of sub-consciously checking to make sure that what I'm hearing was what I was expecting.
You can practice this in your head--start by cutting off your attention when someone is talking mid sentence. Predict where they're going, and then start paying attention again and see if you can tell if you were right. You can also practice it more artificially--listen to a speech, sermon, podcast, or whatever and pause the audio halfway through each sentence and do the same thing. You'll be amazed at how quickly your brain can pick up on the meaning of a sentence.