I found using the thumb plunger from the back did cause some movement artifact. I do feel the electrical release is helpful for hand held at any thing less than 1/250, in my hands. Do you have the thumb plunger?
This is predicated on the fact that I'd only get that camera out for hand-holding because I want bigger, high quality enlargements, than I can get with 35mm.
Lately, I get the most use from the camera shooting Instax.
Flash, is another story. It is always great with flash when hand-holding, due to the stop-action effect.
You might also get attracted to using yours on a tripod. For me, the magic of camera movements led to a Horseman FA 4x5 and ultimately to two 8x10 cameras. It is a slippery downward slope
(now I posted that I see the 985 might not have the bracket to hold the thumb plunger release. )