Depending on the breed and the size of their testes, some are easy to do within the 7 days, some are impossible. Tiny breeds such as Soay really can't be done for about 2 to 3 weeks.
For tricks, we found that the more you fiddle about, the less likely you are to get the band on.
If you don't do it quickly then don't bother that day, because he'll retract them and keep them up there. If when you check afterwards they are not in the sac after all, then cut the ring off quickly as it will hurt him. The scissors on a Swiss Army knife work fine.
Incidentally, banding scrotums and tails in wet muddy weather gives a higher risk of infection than leaving them unbanded.
Yup, exactly the advice I would give, although I do understand your reasons for thinking you would band this year.
Ram lambs aren't an issue until around 3-4 months old, so an alternative approach might be to accept that if you do have problems ekeing out your grass later in the year, the boys will have to go to the store mart. But even though the ground looks awful now, you will be surprised how the grass will grow, so you may find you have no issue keeping the boys and tups in a group from midsummer onwards.
But if you do want to do them, then yes take twiz' advice and get a vet or a farmer to show you how to do it - but not yet, wait until the balls are in the sac when you pick them up.
it does get easier with practise; I've done thousands now and am pretty comfortable and confident with it all. But it's quite hard when you're starting : you don't want to get it wrong, so are a bit hesitant, then the lamb picks that up and sucks 'em back into his stomach, and so it goes. Always check you have two stones after you release the device from the scrotum, and never ever try it without a blade or scissors you can cut the ring off with. Even I, with all my experience, get the occasional tiny primitive testicle that snuck back up as I closed the ring and have to cut the ring off.
I find that my primitive types are not ready before about day 5, and a few go a day or two over the 7 days. The Heb crosses I had were all not ready by day 7. Big fat commercial types can be banded as soon as they've had a feed if you really want; I prefer to give them 36 hours if it's possible.