The methadone that you get from the pharmacy is hydrochloride salt of its free base. Whether it syrup or wafers
In order to smoke, well... really vaporize it. You would need some obtain lab grade ammonium hydroxide, not the shit from Home Depot cuz it has surfactants . That will liberate the free base molecule from its hcl bond, then all left to do is elute into carrier solvent like Chloroform or ether. Lastly, reflux solvent freebase with AC until any discoloration. Then distill off solvent and it will crash out, probably about halfway through and continue to do so until it's a fine, off-white, fluffy powder.
Load yer meff puffer and it's hammer time.