Did you stratify them first? If you did the stragglers should germinate fairly soon, within days, so you don't need to do anything special for them. Assuming they're planted at about twice their depth they should get enough water to germinate with normal watering for the others. If they were not stratified first then the stragglers could take weeks or months to germinate in which case you can either wait it out or carefully transplant the ones that have germinated.
