Use the Bay13 procedure: it is excellent.

1) I happened to have a broken 1" spade drill bit for wood. With the tip and shaft cut off, it fits perfectly. I turn it with a crescent wrench.
2) CAREFUL: You will break this expensive part if you don't follow the correct compression procedure! The Bay13 instructions are very clear, so follow them. The tensioner must be compressed and held in the compressed position with a pin to reinstall the belt. If not you cannot install the tensioner.
3) IPD will sell you the correct belt the first and every time, because they know Volvos. Your local auto parts dealer may have the correct belt at a somewhat lower price, but you may have to visit them a couple of times before you get that correct belt.
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-- Bruce / '82 244 (315k miles!), '86 745, '87 760Ti, '94 854