I’m using my husbands post since I am only a lurker…anyway this morning before I go out for my last ride before my tri on Sunday, I read some of the posts… I especially get a kick out of the one about clipless pedals. SO apparently I jinx myself. Off I go, not a novice rider by any means. About 30 miles in I am at a wierd intersection. I do the balancing act because a car is coming…but he’s nice and waves me on. I realize I’m not going to make it and crash, boom, bang. Down I go! He drives away (good move) I’m so $*)(Q!) at myself. Now I’ve got this lovely patch of road rash (first time) all over my knee with pretty little pieces of pavement in it. How in the world do I get it out? HELP! And no, I have no pictures 
very carefully or just bite down and scrub it out
either way, it’s gonna hurt… I’m speaking for very recent experience
unfortunately the best time to scrub it out was right after - your endorphins are high so you don’t feel the pain as much. If you find they’re really dug in, don’t worry, your body is pretty good at getting crap out. I think I read somewhere the best solution for that is making sure the wound stays “wet”. With polysporin, or those cool bandages like tegaderm or duoderm. I find they really decrease the chances of it scarring. By keeping the wound moist your body can push out the gunk/rocks and you can wipe it away…
Had to go to the ER about 2 months ago (all healed now though) and be treated after wiping out on a turn at 23 mph. I hit some gravel and never had the chance to unclip. The ER irrigated the wound and got the debris out. That was as painless as it comes. Get a spray nozzle and try it. Honestly better than the scrub technique. Good luck. Also use Tegaderm bandages. Work great and minimal scarring.
along with attybiker, i’d go with the water means. only i’d probably do it via taking a bath and thereby softening it up as much as possible, in as pleasant a way as possible, and try to almost float much of the debris off/out. what’s left must be dealt with by hand, of course, but it ought to be much easier, and involve less pain.
peggy