I noticed paint flaking from the bottom of my windows so pulled some of it off. I found that some hard red stuff came away with the pint leaving the gap (brickwork) between the frame and stone sill exposed. I have been told this is trowel mastic and i have to get some and trowel it well into the gap and smooth it off. My question is is there an easier alternative as i have been told the application is quite difficult. Please any advice on application or alternatives.