I have used the washing machine on my trainers in the past, although its advisable to check the wife hasn't left her 'white undies' wash in the machine first!
(I actually thought she bought them in that unattractive,washed out grey, until I tried to buy her some for Christmas....."no no sir , black,white,red yes, grey definitely not".)
Also a quick wash with warm water and left to dry by the bolier works.Can also recommend the old toothbrush for removing mud.