We do exactly the same as Marko with the addition of a quick port film in BH at the 2nd iso position. So to detail the process
1st Iso Position: set up to FB surface, switch over to BH surface, pt takes a breath in, with the pt in BH small late and long shifts are corrected. Pt breaths out. Rads exit the room and coach pt back into BH for CBCT. Pt breaths out while CBCT is analysed. Back into BH for imaging shifts. Treat fields in BH for first iso.
2nd Iso Position: With the BH dicom data for the 1st iso still loaded in AlignRT coach the pt back into BH and manually shift the bed to the second iso position, switch over (quickly) to the 2nd iso dicom BH data and capture a new ref image. Pt breaths away. Flick to BH dicom data of 2nd iso and check delta values are within 2mm. Shift back to ref capture for imaging. Coach pt back into BH, take a quick port to check positioning. Trt if all looks good
Hope that helps!