Using Pot Odds/Implied Odds/EV

I have been reading up on these concepts both on the strategy articles here and elsewhere and I believe I understand the fundamentals of these poker ideas but...

How in the heck are you meant to implement these in practice in online poker? They all require (particularly EV calculations) time that I don't really have, especially if you are multi-tabling. Now some things I have just learnt off the top of my head (potodds for making a good call with a flush/open ended straight draw) for example, but overall I find that I simply don't have the time to judge every case.

Is this something that just comes with practice, or as long as you have a general feel for the idea (like I do with the straights etc), are you doing ok?

I think it comes with practice.
I am where you're at basically, I just use as rule of thumb that a flush draw on next card is close to 20 % probable, gut-shot draw less than 10 %, open-ended twice that etc. What I have difficulty in calculating is the pot odds over two streets, if I got the draw already on the flop.

Implied odds I am trying to factor in as well. It might be that the chips I have to add to the pot is more than 20 % of that pot, but if I reckon villain will bet (or call) again after I hit my flush then the return payment will be more in my favour after that.

For example before the river the pot may be 4000 chips and villain bets 2000 chips. I would have to pay 2000 chips which is 25 %, more than the odds for a flush. But if I hit the flush then villain will give me another 2000 or 3000 chips as a bonus.
Maybe someone can tell if this is completely wrong.

Easy example for implied odds, and easy to remember and you don't need to calculate much. preflop you call a raise in position with lets say 76s. flop comes A84, you pretty much can only win with an 5. the BB is 1$, the villain raised 3x, you call, blinds folded, pot is 7.5$, the villain is pretty much a nit and bets 5$ here, you don't have pot odds, so you should fold. however, if we look at our stacks, both you and the villain have 200$ left, you believe the villain has at least AK here and is willing to go all in.

So, you don't have the pot odds to call here to hit a gut shot, but you have implied odds because you can win so much from this guy if you do make a straight.

Also, it gets easy with time, so easy that in fact, as soon as you flop a flush draw for example, you already know what your pot odds are and with the glimpse of an eye to your opponent you can see his stack and yours and decide if you have the implied odds to continue with this flush draw if he makes a bet that does not give us good pot odds.

i suggest playing 1 table at a time until you get used to it, we all did. and if you just started reading on these odds, you are probably getting too much information right now that is hard to process. but it will get easier with time, much easier.