Hi man,
good to hear that you started mapping
also nice to to have a picture about the problem.
so I can see you using blend textures there going through everything if they don't have a base texture under it or behind it.
I have few tips for you when you going to start mapping on a day:
* when you setting new texture on a brush or patch keep a eye on the texture names:
example: texture_01 and texture_01_blend the texture with the name: _blend on the end are for blending stuff like exploded walls (with a good texture looks really good then for a exploded wall). there are also _wet and many more textures types.
* keep also a eye on the scaling of the texture to make it more realistic.
* make a extra brush between the door way to make a better door way look
* using more textures to improve your map.
* don't forget to use decals on floors, walls, celling, rooftop and many more.
I hope that this will help you out of the problem and many helpfull tips.
best regards,
Gamer9294