Manually forward a sequence - oracle sql

you can just

select seq.nextval from dual 

until it is big enough...

You should determine the difference between the next value of the sequence and the required value. The required value is typically the max value of a primary key column (let's name it ID).

DECLARE
    maxid NUMBER;
    maxseq NUMBER;
    temp NUMBER;  -- without this variable Oracle would skip to query the sequence
BEGIN
    SELECT MAX(ID) INTO maxid FROM MYTABLE;
    SELECT MYSEQ.NEXTVAL INTO maxseq FROM DUAL;
    FOR i IN maxseq .. maxid LOOP
        SELECT MYSEQ.NEXTVAL INTO temp FROM DUAL;
    END LOOP;
END;
/

You can use dynamic SQL to do this. For example, this bit of code will select the next 10,000 values from each of a list of sequences.

DECLARE
  l_num INTEGER;
BEGIN
  FOR seq IN (select * 
                from all_sequences
                where sequence_name in (<<list of 50 sequences>>) 
                  and sequence_owner = <<owner of sequences>>)
  LOOP
    FOR i IN 1 .. 10000
    LOOP
      execute immediate 
         'select ' || seq.sequence_owner || '.' || seq.sequence_name || '.nextval from dual'
         into l_num;
    END LOOP;
  END LOOP;
END;

If you had the ability to issue DDL against the sequence, you could use a similar approach to set the INCREMENT to 10,000, select one value from the sequence, and set the INCREMENT back down to 1 (or whatever it is now).