You can treat the superficial scratches easily. A small coat of even polish can do the repair of the superficial or small scratches. Another method is the blow hot air through a fan or hair dryer and this will remove the scratches safely. Heating up the area around scratches can also fill the scratches.
You can fill small holes with a preheat rod. Heat up the rod from one end and put it in the hole. While keeping heating up the whole from the top end, twist it in the hole until it is filled. Use protection to your hands while filling out the hole area, and once it is filled, patch it up with your hands with gloves on. This will effectively plug the area and then you can polish or use polyester paint to cover the repaired part.
Heat up the welding rod and when it is limp, it is ready for use. Keep the rod about a couple of inches next to the crack, this will fill the crack with the plastic around it. Do not press the rod too hard, as it can damage the boat around the crack area, and then it might not be repairable. Use protection to your hand while carrying out the repair work and then use polyester paint or polish to cover the repaired area.
Make sure you regularly inspect your boat and as soon as you see a scratch or crack repair it straightaway. Leaving the kayak without repair can further damage it and might make it unusable.