Volvos, as I'm sure you understand, are not from Italy (grin).

Most modern head gaskets (from, say, 1970 forward) have any necessary
sealants impregnated into their surfaces and really want to be installed
on a clean, flat, dry surface to seal best.  Adding anything to the mix
will be contrary to the engineers' expectations.  In general, very few
good things have been reported about getting too far from the engineers'
expectations, and this is no exception.  Do what the service manual says
to do and *no more* when installing critical parts like head gaskets no
matter what wisdom Joe (or Guiseppe) might offer.  (You do have the
factory manual or something equally reliable like a Bentley, right?)

Carburetor cleaner (e.g., Gumout) and brake cleaner (e.g., Brakleen) on
a rag both work great for degreasing and both evaporate quickly and
completely with no residue.  Acrylic lacquer thinner also works very
well if you have some handy, but it costs more.  On the cast iron block
surface, a razor scraper should be able to remove the old gasket with
little effort and little danger of damage.  On the aluminum head
surface, the razor scraper is too sharp and will easily carve out bits
of aluminum you would really prefer to have stay attached to the head to
provide a good seal.

I have had good luck with the end of a file, of a type not hatched for
its full length, ground at about a 60 degree angle with respect to the
major axis of the file until sharp and then *slightly* dulled.  It will
remove gasket material without doing much if any damage to the head.  A
machine shop can also dip the head for you at nominal cost, which will
remove the gasket material or make what's left very easy to remove, but
this requires that the head be completely disassembled.

HTH,

JRE