I mixed up 3 oz of sealer. I began by taping off the area where I did not want sealant. I removed the tape as I went. Sorry I did not take photos before removing. I just use blue painters tape so it was easy to remove.
I back riveted 8 stiffeners before running out of sealer. I will bet better at estimating. The process of making the fillets and sealing the rivet heads went well with minimum mess. I cleaned up the machine heads with a bit of MEK.