On 75 and 76 the speedbrakes will deploy automatically if the thrust reversers are deployed and the a/c is on the ground (bogie tilt). At the same time the selection of reverse thrust combined with wheel speed above 90 kts will initiate RTO braking rate (i.e. max avail). This is all automatic. In the event of automatics failing it is important to consider that it will take about 2 seconds for the reversers to deploy so for me the sequence would be : - close throttles whilst disengaging A/T, deploy reversers whilst monitoring autobrake/applying brake, check/manually apply speedbrake, apply reverse thrust.