Yeah the violin rosin looks like and breaks apart like a boiled sweetie too. I try to break it up while holding it in the cloth that comes with it then weigh out by shaking out the pieces onto a piece of paper on my scale.
I've really had some setbacks and haven't gotten an image since the first one. First it seemed like the plates were overheating (after I bought proper 180micron acetate) so I put a fan on the contact printing frame and UV unit, that helped, but the acetate I bought appears to be blocking the UV. I just had a scrap piece of acetate like from toy packaging for the first one. So at the moment there's a plate with the old piece of acetate inbetween the positive and the plate underneath my UV light. Only got about 3 hours on it yesterday so am going to give it another 2 today then see what I get.