I worked on a rust project with one X. If you read some directions on some products, it almost sounds like you can magically put it right over anything. In agreement with others, you really have to clean metal to get adherence-just like you paint anything else-sand, clean, primer paint. I used a wire brush and lots of time. Obviously, power sanders, grinding wheels are good adjuncts used appropriately when needed. I drank the kool-aid and spray painted it. I wish I had known about some of the paints mentioned as it would have been much easier. If you are determined to spray it-you have to do several coats. Rust is porous so the rust converter will sink into it. As such some areas are more porous than others so after the stuff drives, some areas will look very dry compared to others. The dry look just means the spot has not been completely sealed as rough rusted surfaces have more surface area to seal versus a polished or smooth surface. I went back and resealed areas over a few months after doing it. It was doing well at 2 years before it decided to travel upside down on black ice. It's a job of diminishing returns-it won't be perfect no matter how much time you spend so you must resign yourself to periodic maintenance if you want to keep rust under control. From a safety standpoint, put on a respirator and either a shield or safety glasses. You don't want to be inhaling rusty metal dust or having it float into your eyes. Things that don't break down easily in the body , ie rusty metal dust in human lungs, can cause scarring which goes down the road to Chronic Obstructive Pulmonary Disease(COPD) (used to be commonly called emphysema). You can get a N95 mask that can be used with oil based vapors. A regular N95 won't work. You need a R95. Bottom line-think about what it is you are breathing.