Ok theres an easy way on photoshop... this is just to make skin realistin though...
Make a second copy of avatar
On that copy click on Filters > Blur > Gaussian Blur
aply 2px gaussian blur or w/e you want
make a third copy of the original avatar (the one without the blur) put it on top of the blurred one (on the layer section) this way you cant see the blur...
Add a mask to the one thats on top (the one without the blur) it should be white
Grab a brush (circular with blurred edges) and paint with BLACK color over the masked layer... this will slowly reveal what is underneath of the layer and underneath there is blurry skin so it will make it look better
To add blushes you can make a red circle on the right position, set it to gaussian blur and reduce oppasity
to change eye color do the same as with the blushes but with any color you want, buy you will need to set the layer as overlay and then reduce oppasity, this will change the eye color
There is many other things you can do like edit hair and stuff like that but it is a little more complicated, search for tutorials on youtube =)
