I've just mastered the flex no tigers ,no bumps .i used the trowel before but had problems but this time I think from past use it wore in abit and I used no water at all well about a tea spoons worth to clean the edges and I jumped on it soaking wet after speed skim and let it go hard and trowel with it put different pressures behind it and fuk all went wrong . The best way to use them is get through the wearing In stage and then don't use any water wateva so Eva and there sweet