My first 145cm head, a SDH-2 is now being used for fellatio only. The 145cm was my first doll, and I didn't dry her mouth out after kissing her the first couple times. As a result, her mouth developed mildew in the pores of the TPE. That's why I replaced the head, and why I now have 2 aquarium pumps.
Head SDH-2 drying out after our session.
I highly recommend getting yourself fully erect before inserting into the doll's mouth. Use water based lubricant in her mouth and all over your penis before initiating sex. Try to push your penis as deep in her mouth as you can, to push the most air out of the orifice. I feel like I was able to fully fill her mouth and got all the air out. What followed was highly pleasurable, between the suction sensation, the texture of the mouth and throat, and the realistic slurping sounds the head made as I had my way with it. I used the head not attached to a doll while watching hardcore pornography. The orgasm was intense and very satisfying. Cleanup took a little while, still quicker than cleaning a doll's vagina or anus. The mouth sealed nicely around my penis and did not allow any semen to leak out before I pulled out. I recommend a spare head for oral unless you never kiss your doll or if it doesn't bother you. Conversely, I would recommend a head instead of one of the torsos.