1) You could pull the overall gain on the track down (bit under video), and push the fader up on the track(bit on teh left) to compensate. Then, where you want more volume, simply split either side of teh section, and pull the gain back up a bit.
2) Use a compressor with markup gain/output gain increase
3) Split, and apply gain at parts neeeding more volume.
4) split track, and pull quiet sections onto new track and increase volume fader on that track