"Is there any way to reduce the amount of precum? My dick leaks like a sieve even if I'm just horny without a hard-on. If a boner pops I do the waistband tuck but then the pre gets on my shirt."
Some guys would give a right or left nut to produce more because it makes for excellent lubrication. But I get it. Wet spots can be a bit embarrassing.
According to WebMD:
It is also important to know that in some men sperm leaks into precum. If unintended pregnancy is also a concern for you, you might want to consider putting on a condom sooner into activity.
In the meantime, you might think about keeping a folded-up handkerchief with you that you can tuck down into your briefs to absorb the excess.