Lightroom can help, but it isn’t the best tool for heavy retouching like removing softboxes from the frame. For clean, solid black/white edge cleanup, Photoshop or GIMP is usually better.

In Lightroom, try these first:

• Use the local Exposure adjustment, but also adjust Blacks rather than relying only on Highlights.
• If the unwanted area is near the edge, use linear gradients instead of brushing; they’re faster and can be stacked.
• You can stack multiple local adjustments on the same area if needed.
• Use a larger, harder brush where possible for speed.
• Shoot RAW if you aren’t already; JPEG gives less editing latitude.

Also check whether the original capture is close enough to the result you want. If the background or obstruction is too far from pure black/white in the file, Lightroom may not be able to push it cleanly without quality loss.

So: for minor edge cleanup, Lightroom’s local Exposure + Blacks adjustments can work. For reliable removal/replacement of visible softboxes, use a pixel editor like Photoshop or GIMP.