Toothed belt help please

Hello I am currently doing my toothed belt on my r27 but have realised I am missing mot 1801 the locking tool for camshafts, however I do have the camshaft timing tool and the tdc pin. is the locking tool essential? and I don't quite understand the timing tool as the pulleys have to come off for it to go in? will I get away with tip ex? I have the belt fully revealed but do not want to detension and risk the cams moving, any help much appriciated