I'd suggest you start off with 21FBRC into grab. Then 21 to bait. 21~FBRC~F2. Bait a wake up or oki with B32F2 or ex hellfire. Then try 21FBRC~21~flame aura.
What happens is, when the 21 pushes them back, the flame aura might catch them off guard because it will sometimes whiff and if they try to punish, the active frames will get them. If they get hit by the 21 the flame aura will catch them.
All this is theory fighting, mind you, so take it with a grain of salt.
Sit in practice mode and work on your setups. Just don't telegraph your offense or go into a flowchart. Nothing feels worse than an opponent downloading your pressure. Always be aware of your opponent's meter and know your frames.