with AO maps you dont necessarily need a lerp since you want the dark parts to be laid over your diffuse and the bright parts to be invisible so multiply works just as well. in udk the default channel for all texture maps is actually coordinate index 0. 1 is used for the lightmaps, even though that could be changed. But…
Yeah, you can create your shader to use your diffuse on one channel default is 1, and there is a node to change the channel for the AO to 2. Then, on a basic level, you can use a lerp with your tiling texture going into one part, and a constant set to o for the other lerp channel. Then put your AO map into the blend hookup…