When an artist asks "how do you paint reflections?" or "how do you paint water?" or "how do you paint cloth?" they are thinking like proceduralists. They are asking for a trick or procedure that can be used to paint things like those objects.
Procedures like that can be useful for invented objects, and certain media too, with tricks like this being part and parcel of watercolour painting, but when oil painting something it's easiest to never be a proceduralist. Artists paint images, not things. A picture of a pipe is not a pipe!
A tree, a face, a sky, an apple, a pile of cornflakes, a pearl necklace. No matter what is to be painted everything can be done simply and carefully from top to bottom in one layer, using a tiny brush and tunnel vision.
Invented objects can be painted in this way too. For those it's best then not to move slowly but "deeply", forming an amorphous blob into the object. For this, a good visual knowledge bank is needed established by lots of observation.
Those are the only two tricks needed to paint anything.
