Baby oil is not good. Unsafe for condoms and too greasy. I always use lube for penetration, without exception.  Liquid silk is good, very good for hand jobs, but I find a lot of clients go better with a little bit of friction, so I use KY a lot of the time. I put it in with a syringe, out of sight of the client, and obviously without the needle. A glass one is best if you can get one. Just 2 or 3 ml is usually plenty, a bit more if they are going to take longer. I have a lot of regulars and find I can fine tune how much to use on each one. Lubes I avoid are mainly the silicone ones, just glide, easyglide etc. Spills are hard to clean off, wash out of sheets etc and even the floor. One shot of silicone will last three or four clients, so it has that advantage, but I find they take usually longer to finish.