I've also replaced the light seals on my GIII quite recently, using the light seals using the famous light seal kit sold on ebay (is it "interslice"?). There's plenty of seal material left to do some other camera's.
The light seal kit works great, the difficult part is to remove the old seals. I used nafta, which I put in a bottle of eye drops, so you can use the pipet to moisten the old seals with the solvent. (note: don't forget to clearly write the contents on the bottle, or you'll risk to confuse with real eye drops).
But I don't think the cleaning should be perfect. As long as all the old seal material is gone. Any residual glue won't harm the new seals.
Groeten,
Vic