The blog said Ofqual had published two short films, one for students and one for teachers, "to help everyone understand the process better".
Coronavirus: Teachers to rank order pupils for GCSEs
Coronavirus: Teacher assessments will be used for exams
And it reiterated guidance published last week that schools and colleges should "make a judgement about the grade that each student was most likely to have achieved, if they had taken their exams in summer 2020", taking account of "all available evidence including school and college records, mock exams, and non-exam assessment (NEA) that a student has done".
And it said schools must rank all students at each grade for each subject.
"For example, if they judge that eight students would have been most likely to achieve a grade B at A level or a grade 4 at GCSE, they should rank those 8 students from 1 (the most secure/most likely to achieve the grade) to 8 (the least secure/least likely)," the blog said.
It said it was exploring how more support could be given to large schools and colleges where the process of ranking a large number of students could be very difficult.
And it said the cancellation of exams and awarding process for this year meant some of its rules would need to be changed.
"For example, we have a rule that requires exam boards to award grades based only on evidence from exams and non-exam assessments, so that will have to be changed for summer 2020," the blog said.
It said it would shortly publish detailed consultation on rule changes, and that the regulator would need to devise new arrangements for appeals, as well as "continue to explore alternative options for private candidates who need results this summer to progress and for whom a centre assessment grade is not possible; and consider plans for Year 10 students".
The video for students said: "If you were due to take exams this summer, you’ll want to know how your grades will be awarded…They’ll [your school] send the centre assessment grade that they believe you were most likely to get if teaching, learning and exams had happened as planned."
"And for each subject, a list of students at your school who are taking that subject, grouped by grade and ordered by performance."
The video for teachers said: "For this summer’s awards, you’re being asked to provide centre assessment grades for your students. These should be fair, objective and carefully considered judgements of the grades you believe your students would have been most likely to achieve if they had sat their exams."
"They should take into account the full range of evidence available."