I think the 908 slide design is like my 915 (both are 3rd Gen). Does dura-coat require oven curing? If not, I would mask the rear sight instead of removing it. If curing in the oven then all internal slide parts must be considered.

The firing pin block plunger and spring are captured by the rear sight. You can see the plunger from bottom of the slide. Removing the rear sight will "liberate" these parts. Make sure that the coating does not get into the tunnel. Also avoid extractor channel and the firing pin area.

After curing reinsert plunger, then spring from top of slide, remount sight in dovetail (be mindful of the spring when doing this).

Check that plunger can be depressed from bottom of slide and interracts properly to permit or block movement of the firing pin.

It is imperative to function check your refinished / reassembled gun. Any paint residue inside or at outer edge of plunger can affect ignition reliability. Excess paint can affect extractor function.

Good luck, and please post PICTURES when you're done,
Dan