If you find an oiled bird the most important thing to remember is that it is cold, dehydrated and exhausted. It is probably emaciated and is definitely stressed. To give this animal the best chance of survival you must first deal with its present condition. Warm it up, get fluids into it and let it rest in a quiet place. Once it is warmed and rehydrated it may eat on its own accord. Washing a bird in this condition will cause extreme stress and may result in its death.
Washing oil off birds feathers is a skilled task that also involves the re-water proofing of the feathers and should only be done by trained personnel.
Pelagic species such as guillemots and razorbills require very specific environments for rehabilitation.
Contact pauline.beades(at)oiledwildliferesponse for advice.