If you can't dislodge the rust/dirt from the Drain valve,
You can disconnect your bottom radiator hose, drain it run tap water from hose ,
And leave running for about 15 minutes until it runs clear.
Than see if the drain valve works again.
Be sure to re-connect hose and close off valve BEFORE adding ant-freeze coolant of 30-40% mixture (in summer)

__________________
1999 Ford Ranger XL
Vulcan V6, K&N 33-2106 Filter, 3:73 Gears,
FRONT 3'' Susp Lift/REAR 3'' susp.+ 3" blocks,06 Mirrors
31"/10.5"-15" BFG on AR-172 Polished Rims,Smitybilt Console
95 Mustang Saleen Seats,Alternating Blinker MOD
Pioneer CD/iPod/GPS,6.5 Polk Audio/6.5 Sub-Woofers,
Stainless Bed Extender,Throttle and Dome Light MOD,
12" Tool Box,Billet Grille,NightShade Tint,Projector Headlamps
6000K H.I.D. so i can see at night! LOL

JESUS is LORD!