Tidy Wank at Work

While chatting online about sex/penis/masturbation at work, I can masturbate all the way to ejaculation cleanly and tidily by wearing a condom under my underwear. The fit is tight enough that it doesn't slip off after I come. Either I can rub along the shaft through my trousers, or apply extra pressure near the base or apply a squeezing pressure near the base (the most likely place to produce a faster ejaculation).