First, go to Fallout3/data and open the "Fallout - MenuVoices" archive. Find MaleGenericGhoul in the list, and extract all the files.

Find the files you extracted.
 
The following .ogg files can be deleted, along with any associated .lip files:

				followers_followershired_000370b2_1
				followers_followersppurity_00070fb0_1
				followers_followerstactics_0004082b_1
			      	followers_followerstactics_0004082b_1
			      	followers_followerstactics_0004082c_1
			      	followers_followerstactics_0004082c_1

	The first file here relates to Ahzrukhal from Fallout 3, the second to Project Purity, and the remaining files were never used.


Then open "Fallout - Voices" and once again find MaleGenericGhoul, this time just extracting the following files (both .ogg and .lip):

Greeting_00062726
Goodbye_0004bdb8
Goodbye_000a53e5
Goodbye_000a53f4
Hello_0006e8e8
IdleChatter_00089552
IdleChatter_00089553
IdleChatter_00089554
IdleChatter_00089555
IdleChatter_00089556
IdleChatter_00089557  

If you find it easier you can extract everything from MaleGenericGhoul as before and then delete everything but these files (remember you want both the .ogg and the .lip.


Next, open your New Vegas directory and go to data/sound/voice/charon.esp/malegenericghoul. This is where the renamed files will go.

The files will all be named something like: followers_followers****_********_1. 
For ease of reading I have left out these parts of the filenames leaving only the identifying parts, as it is only the numbers which need to be changed. 

For example, "followers_followersFired_0003710a_1" is written below as "Fired_0003710a". Written after each is the new ID number.

The quickest and easiest way I found was to pick each pair of extracted files (voice and lip), move them to the new folder then rename as a pair.

So you would begin by locating: followers_followersFired_0003710a_1.ogg
			    and followers_followersFired_0003710a_1.lip

       and rename them both to: followers_followersFired_00001947_1. 

Continue to move and re-number the rest of the files, both .ogg and .lip, according to this list:

TOPICS;

        Fired_0003710a - 00001947

	FiredNo_000bd050 - 00001948

	FiredYe_000bd049 - 00001949

	Hired_0007fc23 - 0000194a

	LetsGo_000370e6	- 0000194b

	LestGoN_000370de - 0000194d

	LestGoN_00037107 - 0000194c

	Tactics_000370ef - 0000194E

	Tactics_000370c5 - 000027ac

	Tactics_000370b5 - 000027ab

	Tactics_000370d8 - 000027ad

	Tactics_00040830 - 000027ae

	Tactics_00040831 - 000027af

	Tactics_00040828 - 000027b0

	Tactics_00040829 - 000027b1

	Tactics_000370c7 - 000027b2

	Tactics_00040810 - 000027b3

	Tactics_00040811 - 000027b4

	Tactics_000370d0 - 000027b5

	Tactics_00037109 - 000027b6

	Tactics_0004081b - 000027b7

	Tactics_0004081c - 000027b8

	Tactics_000370f5 - 000027b9

	Trade_000370c3 - 00001669

	Wait_000370d7 - 00001668


Greetings;
	
	Greeting_00062726 - 00002a97

	Greeting_0007fe02 - 00002a98

	Greeting_00089462 - 00002a99

	Greeting_00037130 - 00002a9a

	Greeting_00037131 - 00002a9b

	Greeting_000302ec - 0000194f


Goodbye;

	Goodbye_0004bdb8 - 00002a9c

	Goodbye_000a53e5 - 00002a9d

	Goodbye_000a53f4 - 0000361b


Hello;

	Hello_0006e8e8 - 00002a9e

Idle;

	IdleChatter_00089552 - 00002aa0

	IdleChatter_00089553 - 00002aa1

	IdleChatter_00089554 - 00002aa2

	IdleChatter_00089555 - 00002aa3

	IdleChatter_00089556 - 00002aa4

	IdleChatter_00089557 - 00002aa5


So, thats a total of 41 files renamed. You should now have a fully voiced Charon.
Combat and other generic speech is handled by the games existing MaleGenericGhoul files, hopefully this will blend in reasonably well.