I actually don't TS for asking this, the first double you learn is usually the drop step to get the motion down, then they move on to blast doubles and other fun stuff once you have some motor patterns built up.
also just do the royce method its so sad how far jiu jitsu schools have gotten sway from real fighting thats why people diss jiu jitsu today saying ohh its just a sport ground fighting it sucks for self defense the basic knee stomp to clinch body lock or trip works wonders