It should work similarly, amphetamine sulfate is probably a little more soluble in methanol than acetone, but still should be poorly soluble. So you'd just dissolve the oil in methanol, do this by adding methanol step wise, to get as little of it as possible, (minimum solubility), and then add drop wise your H2SO4 until pH 6, but yo should see precipitate already around 8-9. If your H2SO4 is dilute though it won't work well since the salt will partially go into the water (but whit sulfuric this shouldn't be as bad as with HCl, since amphetamine sulfate is less soluble in water than hydrochloride salt)
If you though feel like you miss a lot of what you had before, do evaporation, although this would be kinda hard whit the H2SO4 being a liquid to get fully dry (consider neutralizing because of this)
