Ok someone told me I needed alpha textures to help blend brushes, could someone please explain to me what alpha textures are, and how to make and use them?

Thanks in advance

Sounds like the HL2 engine firstly.
Select the face of a brush or brushes and open up the material manipulation tool. Select a material with, say, grass and gravel ( I forget the speical attached name for them). Then go to the tab with the displacement stuff and click on the alpha painter button. Now just click and drag around like you would when displacment mapping, the material should slowly cycle from grass to gravel. Sorry my hammerrs buggered I can't be too specific.

To make them, you need a new channel in photoshop, which you will pick from one of the RGB ones.

You then hit ctrl +L to bring up the levels options, and you fiddle around till you have the effect desired. Remember that all that is black in the picture will be transparent in game and what is white will be completely visible.

Add some effects, depending on the texture you're making by deleting some of that new channel with a brush

Save the 4 channels in a 32 bit TGA file (only that will work, 32 bit is required for transparency) and put that new file into Vtex. Voila

or just find a nice tutorial on www.interlopers.net

This video (http://halflife2.filefront.com/file/HalfLife_2_Displacementmap_Tutorial_Video;40427)

actually has a quicky on using alpha textures. Give it a try.. It's towards the middle of the video or more.