Doing successful blasts on new websites

Most people warn against doing blasts (scrapebox/xrumer/etc) on new websites, but a percentage seem to do it successfully and rank, or at least know when to stop. And some people completely deny the existence of the sandbox penalties.

What's your take on the matter?

It depends on many, many factors; size of blast, type of blast, whether you ping, your niche (most people seem to agree that any new gambling site will be sandboxed at least for a while almost automatically) etc.

I have few noob questions

1.How does scrapebox improve my PR ?
2.Same as the OP...What proposition i can use xrummer and scrapebox and pinging to get a new domain to top position.

Thanks in advance