If the pitches are longer than half a rope length, either:
Get the second to tie into both ropes and re-clip the trailing one behind them. Third is tied into the trailed second rope. Then you bring them up separately. Third cleans the draws.
Or you tie in to both ropes and lead as if on half/twin ropes (use twin-rated ropes if you have them), then have both seconds climb simultaneously, 15m or so apart on separate ropes. Use long + short draws on the bolts to clip separately for singles/halves, or if the rope is twin-rated just clip both ropes to the same draw EVERY time. More work belaying them for you but quite a bit faster. Second/third only unclip/clean their own rope. The third needs to maintain that 15m separation to avoid getting clobbered on rope stretch if the second falls.
Practice lowering seconds on a guide plate first ;-)