The term "curl" refers to the dumping motion of the bucket. Curl the bucket forward(dump) until the leading edge of the bucket is at a good angle to the ground like a blade. You can then push the joystick forward, putting pressure on the leading edge of the bucket. This usually raises the front tire off the ground. You don't have to raise them that much, as it won't add any mre weight to the leading edge. Then you can back drag and use it as a scraper to pull the high spots into the low spots.
Another tip for leveling off a small hump is to lay your bucket flat on the ground, then curl it forward just a little(you'll have to get experience as to how much angle to use) then drive forward with the joystick locked and you should scrape off an inch or so at a time, depending on soil type, etc. If your tractor can handle more, you can take more aggressive angles. The material will fill the bucket, which you can then take to the low spots and dump.
Once you get some material into the low spots and you want to level it, you can curl the bucket back toward you and use the rear or underside of the bucket. Move the joystick all the way forward past the detent until it clicks. This is the float position. You can then back drag over the fill material to level it out with the rear of your bucket.
Float doesn't work well when going forward if you are trying to remove material. It tends to make the tractor ride up onto the loader. Float does work OK if you keep the leading edge of the bucket off of the ground a little, like in snow removal.
I've got some videos of my loader in action on my homepage. If you want to look at them, they demonstrate some of these techniques. You can see them by <A target="_blank" HREF=http://pt425.godollei.net> by clicking here </A> and then clicking on the videos link. Scroll down to the small tooth bucket section. They take a while to download and are kind of grainy, but you'll get the idea. They require windows media player to view.
Hope this helps. /w3tcompact/icons/smile.gif