The Fudebakudo Bloodhunt™

Preparation:

Place a small spot or smear of red ink (or blood if you really must) in a discreet location on your keikogi where it can pass unnoticed until you have need of it.

Application:

When time needs to be wasted, "discover" the blood on your keikogi and, feigning concern, scrutinise your partner in careful detail for a cut or graze.

Pros:

This is one of the most subtle and sophisticated time wasting techniques, and should appear to be entirely for the well-being of your partner. If applied well, unsuspecting partners may even continue scrutinising themselves while you take a breather.

Cons:

In the event of real bloodletting, previous application ("crying wolf") can work against you.
Also, note that this technique cannot be applied in any dojo where keikogi are routinely splattered or drenched with blood. In general, if there is a "Blood-borne Pathogen Policy" posted on the dojo noticeboard and a pair of rubber gloves lying on top of the first aid kit, it'll probably work. If the members of the dojo routinely bite each other and wear bloodstains like badges of pride, it probably won't.