On the single pin 8 footers, just cut ballast out and wire everything on one end to your hot wire wnd the other end to the neutral.
on the 2 pin 4footers, cut the ballast out and wire the left side of the 'tombstones' on ONE end to the hot wire and the right sides to the neutral. The other end of the fixture is left unhooked (just be sure you have non-shunted tombstones)