I usually give them two days, but I think I'm pushing it.
Lately, rusing things along a bit for group build deadlines, I've put oils on a model as a drybrush/highlight coat, let them dry two days, and then put the gloss barrier coat on. Often, the barrier and the flat that follows it will cause the oils to loosen up. So far it hasn't been a big problem, but still it has me concerned.
How long do you guys let the oils dry before you proceed with washes?