I'm likely to have to commute to somewhere that's less than ideal for security. The whole thing is less than ideal but it's only for a couple of weeks.
Using using the beater bike I already have isn't an option: it's 23 km under time pressure, and sometimes I'll have to use the hybrid with child seat (and try to get there in 55 minutes). I'd rather use the tourer if I don't need the child seat. In either case I'll take two locks (probably one D-lock and one cable lock, possibly 2 D-locks). There are some fairly solid iron railings to lock up to, and both bikes are already security marked and registered.
So as an added detterent I'd like to make the bikes look as undesirable as possible -- how can this be done in a reversible way? While Reduce Resale Value to Avoid Theft? (Uglify) is closely related, the answers there concentrate on permanent approaches, and I'm specifically after something more temporary.