Boat Bling's line of "sauce" products are very high quality if you want to buy something that is ready to use, but I am not sure how well they work on something that has been neglected. If the RTU products won't do it for you, for the soot on the transom, you can use Simple Green degreaser(diluted), but it tends to strip wax and polish. For the water spots, if vinegar/water won't cut it, you can step up to a mixture of pool acid and water. You will want to play with your mixture and only use enough to do the job, though. Both vinegar and pool acid also tend to strip off waxes and polishes though.... As always, I recommend that you avoid products containing carnuba wax, especially on white gelcoat.