ive never heard of WAFER'S???
anyhow, im on Methadone , have been for 5 years and Heroin before that for 10 years
best to wait until you feel really bad - no less than 24 hours after last dose of Heroin/Morphine...
If your just on £10-£20 worth of Heroin a day then that 40ml will be enough... however, if you have a massive habit you may need more...
they used to say that you get 10ml for each £10 bag of Heroin you have per day... so 6 bags a day would equate to 60ml Methadone 1mg/1ml
But
that was many years ago when street heroin was of much higher quality than it is now... now your lucky if you get Heroin more than 1% pure, my friend who has been injecting it for 15 years says it does nothing now and his Methadone holds him - it went that way for 1 year for me before i decided to rap it in - smoking it would just yield a sore throat and bad head - injecting it wouldnt be much better either....
I done a full withdrawal off Heroin using Methadone in Jail and it worked really well and went like this:-
after £40 day habit I had nothing for 48 hours and i was really cold-turkey, then 30ml of Methadone sorted me out and even gave me a buzz..... this was reduced 5ml every 2 days until you finished... it worked a treat - slight withdrawal afterwards but managable