chain-whips, 2 of them, are all you need. If you don't have then borrow 2 for a half hour, max. You won't have to use them to re-install afterward.
EDIT, sorry but did not see the pic when Iadvised you , it IS a freewheel and not a UG cassette, so the chainwhips will do nothing (unless you want to take sprockets off the FW body). You need the FW tool to remove it, as others have said... then you can soak it in a can or solvent (try 50-50 acetone and ATF) then drain-dry and re-lube with liquid lube.
Last edited by unworthy1; 07-15-17 at 12:53 AM.