Sure. Just mix it in. I've found that a bunch of it just sticks together and becomes clumpy.

No!

Cedar is not a good sawdust to use as a mulch, as there are allelopathic chemicals in the wood that may make plants unhappy or worse.

In general, sawdust tends to make N unavailable as the soil critters take it to break down compounds in sawdust, esp when worked in. You'll want to watch and ensure this doesn't affect any N-dependent plants where the mulch is going and supplement N when needed.

Dan

I have used Cedar wood chips and Cedar shavings as well as Cedar sawdust as mulches and have seen no problem with the plants I want growing. Mixed with other material is better, especially the sawdust since it tends to clump when wet. Just keep in ind that a mulch goes on top of your soil not mixed into the soil.