I'm not great at building booters but this is what I've learnt from others...
Take a long knife or saw, so you can cut blocks of snow. Even better, some backcountry shovels come with built-in saws in the handle (i.e. saw pulls out of the shovel cylinder). Being able to cut blocks of snow makes a big difference!
For best results you want to leave the booter overnight to harden. This way you're not spending all your energy building the booter before hitting it anyway. Doesn't hurt to sprinkle salt over it either (causes a bit of melt then freezes hard over night). You can then re-shape and groom the next morning to get it 100% ready.
Honestly, that's about all I've got for you, but hopefully it helps.
Don't forget to take photos!
