how to merge textures?

I am trying to figure out how to “merge” two textures together with the same object (the same mesh). I know how to apply different textures to the same mesh but it leaves a hidiously visible boundry…knowticable I mean. What I am looking for is how to get them to gradually mix together into a smooth transition.

If anyone could offer some advise and explain it…I will forever be in debt!

Stencilling?

http://wiki.blender.org/index.php/Doc:Manual/Textures/Options/Map_To#Stencil

You don’t give an image of what you really want so I’ve included this link as one way to merge textures.
http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Landscape_Modeling_II:_Texture_Stenciling

I’ll try to paint a better pic here. Imagine a sculpted model of a face, ie. one mesh, I would generally use one main skin material. However on the right side I want a scar using a different texture and tone but only in that one spot. How can I use the scar material and texture so that it has a “smooth” transition into the normal face material, what im saying is that how can I apply the scaring so that it doesnt look like I taped it onto him!

I hope this makes more sence.

Thanks for your patience…this type of problem is really confusing to me.

Thank you Richard, I have another post for you to read if you would be so kind. Being new to BlenderForum here I was not sure to reply dirrectly to you or where I did!