Having established which rads are cold, make sure the 3-port valve is set to a position to enable CH (in other words, CH=on, water=Off).
Then use the pressure of the pump to push the airlocks along. As soon as one reaches a rad, the air rises to the top of the rad and no longer remains in the pipework. Bleed air out from the top of each rad in turn, ensuring the lockshields at both rad ends are open. (Take a note of how many turns of the fixed-position lockshield are required to open it up, so that you can rebalance afterwards back to the same position).
If that still isn't pushing the air out, turn off some of the rads that are working normally using the lockshield.
The pressure of the pump will always be powerful enough to shift air along the pipework system, especially if the circulating water has no other place to circulate other than the non-working rad circuits.