Mud/silt in door sills - how to get out?

[atlantaM3]

so a while ago went through some mud that was deeper than expected. Today I pulled my slider off to clean up, and there is mud on the backside of the bolts. Is there a way to flush out the inside of the sill to get this stuff out? I am planning on keeping this for a really long time, and don't want the sills to rust out.

Any advice appreciated on this one.

James