I would not use paint thinner as it will leave a residue that could interfere with the new application of thermal paste.
If you have old thermal paste or, worse, one of the thick pads use a razor blade to remove most of the goop. Then use lacquer thinner,or one of its ingredients acetone or toulene, to remove the rest of the residue. You can get
these products in pint or liter tins at the paint store.
Once this is done start the procedure as outlined on the thermal paste web site.
p.s. the tabs on a razor blade do an excellent job of "lapping" the thermal paste
Hope this helps
EP, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS