It does handle like a brick when heavily loaded, so I take out the Air Defence Systems first; if I have the "Heavy" weapons like the Kh-25ML or Kh-29T (which is also fire and forget, so you can concentrate on your next target after you fire it without having to stay lased on a current target) I try to use them first (unless you need them for a bridge or building). Once they've left the rails, try to use up your bombs and then you're left with just the Vikhr (for example), and you are a lot more manouverable (keep an eye on your angle of attack indicator, if you go over the limit around 20-25 degrees you start to stall/depart flight envelope, so ease off on your joystick back-pressure. You can also use rudder to keep the ball in the centre so you aren't slipping so much - more efficient use of your control surfaces). This also improves your fuel consumption so you have more loiter time and can make more passes. If you use all your Vikhr's, eject the empty magazine and use guns.
When using the Laser, as soon as your target/targets is/are destroyed, switch the Laser off straight away - the less time it is on, the quicker it cools and allows you to start your next attack run sooner. That said, extending away from the target zone whilst the Laser cools for longer time periods also gives you more time to sort out your attack run and allows you to take out more than one target. (Patience is a virtue, I found after flying the A10, I need more time to sort my s**t out when lining up and designating targets in the Su25T).
The last tip I can give is if you are firing the "heavy" weapons, engage the Auto pilot for a short while before firing, this then sorts out the trim for you in a couple of seconds and you can then disengage the Auto pilot and carry on flying with relative ease.