Do you have a rotary or a drop spreader? A rotary is better for that kind of thing, although you can prepare to get rather brown doing it. Wear old pants. :-)

If your amounts are small enough, do it by hand. That works, too, and less or more here and there doesn't matter much with UCG.

Yeah I guess it is the rotary kind. It is from Scotts and it drops the grounds to a round saucer like thing that shoots the grounds/fert to the lawn.

I just fling the grounds around the lawn by hand. You don't need to get a perfectly even distribution the way you would with chemical fertilizers.

I'm not sure what UCG is but if it is a ground grain, these organic materials tend to absorb humidity from the air and clump together. The little roller in the bottom of a drop spreader will dig out about an inch but the rest sits on top. I used to bounce my spreader to get it to drop. Hmmm, that reminds me, that's probably why it broke. Broadcast spreaders aren't much better at releasing the grain but could probably be modified to stir it down better.

UCG = Used Coffee Grounds

Yeah, when I was using it, I had to just fling it around by hand. And, that really works pretty well, if a bit more work.

But, in my climate, it got so water repellant, I gave up on it and just went back to grain meals.

Mixing them with a dry grain like soybean meal would work. Perhaps a dry sharp sand would work too. Percentage wise would probably depend on moisture content. I've been toying with a way to spread compost by spreader which has the same issue.

I spread my UCG by hand (small yard) - BUT be sure to use a glove. You can get a good caffeine buzz going using your bare hands...