Singe sided bats. If there really isnt too much of the old stuff
remove it. If there are animal dropping etc, take care of that first.

Then seal up and electical holes that you may have. What I mean
by that is high hat or outlet drops that are in the ceiling.

If you do have highhats up there make sure that they are rated
to be up against insulation. If not, the need to be simply boxed
in. (no need for any fires up there)

Do NOT insulate the roof!!! This can create an icedam situation.
This may work for warm weather areas, but you are in canada.
If your into doing all of this, go to one of your local home centers
and simply ask for help.

One thing that I certainly recommend if you do this is that you
get decent dust masks (respirators) when playing with this
stuff. No need killing yourself while saving some money!
Long clothing also helps releive some of the itch factor.

Tom