Whenever I brake through the clear when sanding, I'll scuff it, take some featheredge tape (masking tape that is folded in a little on the sides) and outline 3" past the brake through completely around the area and cover the rest of the panel. Next, I'll shoot the bc on the area to cover, remove the featheredge tape (you'll notice a very small tapered edge), then lay two last coats of clear on the whole panel. The best thing to do is to clear the whole panel. If it's on a quarter panel (no natural breaks/cutoff points) where you need to blend, before you shoot the clear, lay the featheredge tape on the top-edge of the sail panel/roof and cover the rest past it and anything else from overspray. Next, shoot the panel, first coat ending 3-5 inches below the featheredge tape. When applying the second coat on the panel, take it all the way up to the featheredge tape. Remove featheredge tape and let it cure overnight before buffing the blend on the edge.
Hope this helps.