Just saw this, and could not help myself but to post...
The guy that is doing the included video is obviously not a professional painter, and there are some inaccuracies, I would find a do-it-yourself painting forum instead, but just in case anyone looks at this, please disregard the information in the video..
So... If you are using a house paint that says either latex or acrylic, then it is more than likely water based paint, in which case you could use anything that says latex paint extender to slow the drying time, so that it's easier to work with, and has more time for brush strokes to level out of the finish before it dries... It also helps if you are painting large surfaces, so as to help keep what we call a "wet edge". Basically, you don't want to brush back into paint that is partially dried, because it will "flash" (make a dull spot that shows brush strokes where you have overlapped with wet into partially dry paint)
However, if you have a paint that says acrylic but smells exactly like fingernail polish, then it could be some sort of cross-link base, or acetone base, so you should always check the label of the paint under "Thinning and Clean up" to be sure whether it is water-based, or some other type of base...
By the way, acrylic or latex are just different types of synthetic resin, this post is long so I will not compare and contrast the two here... But know that there is another water-based cleanup synthetic resin which is called "waterborne" it was basically designed to replace oil based paint, and has very high adhesion, so with a light sanding, you can use it on something that was previously painted with oil based without necessarily needing to use a primer between... If you add some extender to it, it really levels out and sort of looks like oil, but you must work quickly and keep the wet edge that I referred to above...
I've used both Floetrol and M11 as extenders. M11 is colorless and watery and will thin out the consistency of your paint as well as extend the dry time...Floetrol is translucent and syrupy which will extend the dry time without thinning the consistency of your paint...
One more thing...
The guy in the video says that mineral spirits is an extender for oil-based paint. This is completely wrong... Mineral spirits is a thinner/solvent for oil-based paint. If you want to extend the dry time of oil based paint, you need an oil-based extender such as Penetrol...
Jeez long srry..