In World 6-2, get on the back of your enemy Albatoss and start on your loooooong night journey. If you fall off, you're done for. But you can move ahead so much easier this way, compared to leaping across waterfalls on Trouters.
(1) Make it across with a Power Jump. As soon as you enter World 6-2, you may find that the wall before the exit to map B is a little too high for a regular jump. If that's the case, hunker down to charge up energy for a Power Jump, and you'll make it over.
(2) Albatoss airlines. Once you come out, you'll find yourself on the edge of a steep cliff. At your feet here is only one clump of grass. That, and an army of angry Albatosses flying straight for you. Get moving and make a daring leap to land smack on their backs. They will carry you toward the goal.
Don't fly unarmed. It's not a bad idea to pull up a vegetable before you jump on an Albatoss and carry it with you. It might come in handy if you're threatened in midair.
(3) Sub-space. When you reach the cliff with two clumps of grass, hop off the Albatoss. The potion lies in the patch of grass on the left. Enter Sub-space here and you can get a Mushroom. There's won't be any more Albatosses flying to the right. So when you come out of Sub-space, get on one flying to the left and go back to the start of map B.
(4) Look out—danger ahead! The action at this point in your flight could be tense. You will encounter three Albatosses lined up in a column flying right for you. Jump over them before you collide with them. Luigi can safely make the jump without charging up if you time it just right. For everyone else, it would be a good idea to charge up a Power Jump ahead of time, and be ready to use it when the time is right.
Fly low for A-coins. If you want to grab all of the A-coins, you're going to have to travel along some fairly dangerous routes. Two of the coins in particular are positioned very low in the stage. You'll need to find an Albatoss that's heading back to the left low enough to collect the coins and keep on flying. Of course, you can always just sacrifice one of your lives collecting them if you'd rather just get it over with.
(5) Mean old Birdo. The mini-boss of World 6-2 is Birdo again. This nasty character doesn't give up easily. She really goes looking for trouble. Meet her flaming throws with the Mushroom Blocks above and below you. Drop two directly from above. Then throw the other at her from the left. That should take care of her for a while.
After defeating Birdo, grab the Crystal Ball and head through the hawkmouth gate.