Penis plugs, and sounding/related practices in general can be very sensual. For the inexperienced, some thoughts:
- in plugging and sounding, generally anything inserted into the urethra, cleanliness is really important. The penis plug or sound should be clean, ideally sterilized. You should also wash the meatus thoroughly (mild soap and water, or diluted Betadine work well)
- fit (diameter and length) are important. My favorite penis plug combines a glans ring (helps the plug stay in place during vigorous fucking), the 'knob) that forms the plug itself, and another 'knob' that is intended to stimulate the wearer's frenulum, and the partner's posterior vaginal wall. This plug is comfortable to wear, and doesn't produce significant risk of either retrograde ejaculation or bending injury
- longer sound-style plugs, particularly solid versions can be uncomfortable, and in some cases may prevent your cock from bending/flexing during penetration. Solid variants, especially large-diameter versions can increase the potential for retrograde ejaculation - not necessarily serious, but not necessarily pleasant
- there are hollow, "cum through" variants of the penis plug/sound that reduce the issue of retrograde ejaculation - they provide enough "back-pressure" for pleasure, but don't retard ejaculation sufficiently to forse semen into the bladder