You can find the Photoshop oil paint filter in the filter menu and stylize.
Select any image or a layer or a smart object (such as a shape or type) and apply
There is a preview but that is very small but you can also turn on the preview option and you will see the effect added to the current selected design, image or layer. You have the following settings available : brush stylization, cleanliness, scale, bristle as well as lighting and angle and shine. Scale and bristle detail do nothing unless you check the lighting and also you can then modify the angle and shine. It has recently been updated so it is now a lot faster on the mac.
It should be noted that the effect is pretty decent but it does stand out with the same result if applied only once or twice, you can see the effect applied to many images on the web as well as in magazines and art books and the result is often very same though with some tweaking you can create a lot great variety than a one click approach. It gives the impression of a slightly swirled oozing paint but the underlying design is repeated and also cannot be altered. I really hoped that this tool would get an update and allow for a great range of source designs as well as some randomization throughout the design as well as overall randomization.
Always find it works well with smaller images, and only sometimes with very large images. With larger images, you really can't see the result at all unless you apply it many times. It does really seem to depend on the size of the image
Set the cleanliness very low and the stylization high and set the lighting on and change the angle and set the shine high and the scale low, you can create an interesting intense noise with any image. Apply it a couple of times via the repeat to create some very unusual color penciling. You can also apply it to a duplicated layer and then use the blending modes in the layers panel with the original image. Works also well with combining it with a basic low setting of the Gaussian blur to create an odd grainy image. You can also create unusual psychedelic effects using add noise combined with the effect applied multiple times and then modified by adjustments such as vibrance (set to the max) and levels to brighten up the image.
You can use it multiple times with the same settings so select a layer and then use stylization high and cleanliness high and keep the lighting off and you can create a lovely smooth flowing smeary design in seconds. This also works well with adding some noise via the add noise and then repeating the effect multiple times smearing the original image along with the noise. Combine that with adjustments such as vibrance and levels and all kinds of psychedelic imagery can be created. You can create all kinds of unique imagery by using the effect more than once and combining it with others such as blurs etc to create swirly smeary imagery etc
You can limit it to part of an image by using selections such as the rectangular marquee tool found in the tools panel. You can also use selections via the select menu. You can also use the image after you have applied the effect and use selections then.
The lighting option can be turned ON, not that keen on the result as it depends on the contrast of the image, the blurry regions end up with this swirl of noise around the sharper parts of the image. Set the cleanliness to the max and it is sort of fine, set that value low and it is an ugly noise effect. Stylizations makes a subtle difference. Set the scale low to get finer lines, set it to large to get a more chunky effect. Low bristle setting and you get a blocky look to your image. Works best if you set the shine to a fairly low value. The angle is useful for embossing of the image. Once you are happy with the lower settings, you can always re-apply it multiple times via the repeat. Also, once you are finished, you may like to re-run it with the lighting off and repeat that and that makes a very nice smeary paint brush like effect in the image with type etc. If color is involved in the image, you may like to go to the image menu and adjustment and vibrance as I find the image gets a little duller with re-applies of the effect. It is a pity that is not proper lighting with multiple lights as that would be a wonderful addition.