Hello... Yes.. you can follow the procedure as long as you are maintaining the hygiene. Although expressing good amount of milk is straining and takes lot of efforts and can even lead to infections.
Next Steps
My advice would be continue breast feeding alternatives with expressed feeding while slowly shifting him on other feeds after he turns 6 months.
Health Tips
It is difficult to get rid of bottle feeding habits.
hope this helps. kindly consult for other nitritional queries if u find this helpful.