Reference, "Riote Kanoha Gaeshi," Dennis Palumbo, Secret Nidan Techniques Of Hakkoryu Jujutsu, Paladin Press, 1988.
Step 20-22 of H. Yondan is the sequence of three reinforced blocks (morote uke). All Heian performers and most Pinan performers do these three steps in exactly the same way.
A moment before, in step 19, you had hold of the opponent's hands in riote kanoha gaeshi. This means you had a te nage wristlock applied to each hand. If you maintain this hold, you can use it as a come-along, forcing the opponent to go where you wish. If you maintain the outward rotation of each wrist and push on both wrists simultaneously, he'll back up. If you vary the pressure, you can steer him like a wheelbarrow. Steps 20-22 may be best explained as "driving" the opponent through the crowd, using his body as a shield.
If you subdue the morote uke stackups and just keep your hands strongly in front of you during these three steps, your motions are a good approximation of the "wheelbarrow" technique.