if the seal has been sitting on a shelf for ages or in the sun they can go hard and oil itself wont make them nice and soft and fluffy. Stop smoke or stop leak in your oil even a tiny bit works pretty darn well.
I have bought motorcycles that have been in storage for 5 or more years that leak like a Indonesian illegal vessel and a capful of stop smoke/leak in the crank case fixes it in the next ride. Never to be needed ever again. When i fit rear mains I make sure they are nice and fluffy if they aren't you can rub stop leak right on the seal. Also I use a socket on an extension which has been put on backwards which is the same diam and tap the socket with a mallet and get it in straight.
If you put it in at an angle and catch it straight it makes it squiff and will probably leak prematurely. I have never put any lube on the inside of the seal. The engine is full of oil. The seal is in direct contact with oil. Only thing any kind of lube would do is make it easier for it to be cut on reassembly.

If it makes you sleep at night go ahead.