Oil Painting Tip(Underpainting With Gesso instead of Acrylic)
I have heard of a lot of people doing their underpaintings with acrylic and then completing the painting in oils. I have done this too in the past because it dries so much faster than oil. The advantage of an oil underpainting as opposed to an acrylic one is that the oil paint will absorb each subsequent layer better than the acrylic.
Also when you attempt to paint over the acrylic layer the oil layer on top of it will seem dry but as you trying to build on top of it the paint pulls away, you can actually see a height difference. This is probably because of the nature of acrylic paints. They dry slick and aren't porous like oil paint is. The layer you place on top doesn't sink in properly to truly bond with the underpainting.
An easy and effective alternative to acrylic underpainting is just using black and white gesso to do the underpainting. It has the same drying time as acrylics but is more absorbent. It gives the surface the tooth that acyrlic doesn't. If you want a smoother surface you can lightly sand the dried underpainting with a fine sandpaper. Just make sure to dust it off afterwords.
I recently started doing this and it has worked out a lot better than acrylic. If you are doing the underpaintings in colored acrylics I would suggest adding gesso to them to improve the absorbency.Not only has this helped keep the first oil layer on top from peeling or scraping away the oil paint seems to dry faster.