Yeah its best if the dope is in soluble salt form.
WHAT salt really does not matter a damn, just as long as the acid/salt itself is a physiologically acceptable one. I.e nontoxic, and also you don't want to use TOO strong an acid, or something that will specifically damage whatever drug it is that is being used.
Much dope in the UK is intended to be smokable, and its the responsibility of the user to salt it themselves using E.g citric or ascorbic acids the two most common ones. But anything nontoxic and that will not damage the drug will do it, or more or less, you of course need the acid itself to be able to dissolve, so the likes of big, oily, greasy nonpolar zits like a long, long chain fatty acid isn't practical.
Don't usually need to with the gear I use by preference but this is not the standard at all.
Its easier by far for your average street dweller and junkie to add some mild acid and render dope made from the outset to be suitable for smokers to use than it would be for a smoker to do the inverse, starting with H acetate, HCl etc. and titrate to freebase form, back-extract it using solvents which of course will always lose a wee bit even if your damn careful and your technique is on form, solely from such things as transferring powder/solution from one vessel to the next.And of course one then would need to work up the freebase, potentially add caffeine etc. to make it fit to be smoked, evaporate the solution and then use it. Whereas salting out heroin base all one needs do is add acid solution, sometimes heat it a bit, draw up, ensure neutrality and whack it in there. Most smackheads aren't known for their lab technique.
2ml? thats bloody small and fiddly. Not as bad as 1mls though I hate those, hate em, hate em hate 'em.
And weather or not that size will do is relative to the user themselves and depends entirely on how much they can dissolve in the solution, and how much solution they must then inject. I have to use 5ml barrels, and gently warm the stuff to ensure, for ex. with morphine sulfate to be able to get enough of it in solution so as to be able to get where I'd like to be, because the solubility limit at RT is 60mg/ml in the case of either sulfate or hydrochloride (morphine I mean not H), but 5ml of saturated solution is borderline. But for someone w/ no tolerance at all it might well be enough to kill a naive user.
I don't know. Are you a man, or a mouse? a house sparrow? the shade of michael jackson/a gorilla (pretty much interchangeable in the last two cases although jackson probably didn't include nearly so many insects, bits of tree bark, shrubbery et cetera, within his diet mind you and definitely lacked most of the fur, dark or silver, and most of it was on his head I presume, can't say I looked elsewhere and cannot claim to ever wish to for that matter) or somewhere in between? you could be anywhere from Drosophila to blue whale and we haven't got the foggiest. So only you can answer that one knowing your tolerance and the quality of the stuff you intend on using.
Just ask for a measuring syringe at the chemist, they aren't very expensive, can't put a needle on one without hacking it a bit, you just want to feed your pet....well pet whatever it is you want to feed. Pet shouldermonkey probably (nasty, intractable creatures, need chipping too, ideally, with a false address so if it gets lost it doesn't wander home again

) The back-ape that is not its food. Can be expensive to keep, the vet bills for those things are awful, and they eat and eat and eat and eat until they puke, give the fucker an angstrom and he'll take a parsec.
Probably though I'd think, whats the tolerance like and the gear? Generally speaking though, dissolve it, draw it up, no need to filter (well really, no need for it to be free of particulate matter, or sterile either, after all think what that thing evolved for.)
Then if you need a turd, go have a turd, and insert rig, depress plunger, light cigarette. Enjoy dope, enjoy coffin nail. Repeat as appropriate, Do remove the needle first. And it helps if you take the rig out when your finished and refrain from vigorous breakdancing for the next half hour or so. The reason if there anything unmentionable using the place as a squat (pun most certainly intended), dropping one before administering the gear is because if you have to bust a fudge and don't do so, then it can play the role of a sponge, absorbing perfectly decent gear. And I don't think you want to have to encourage it to leave its burrow by waving a copy of The Sun outside your sphincter (and even LESS so inside), dry it out, roll it up and smoke it (this has a name. That name is 'soapbar'

). Should kick in pretty quickly, its roughly as efficient as the equivalent drug via IM. Although there is no rush it certainly does have a much quick onset, and bioavailability of oral H would be abysmal. Should feel the first onset within 5 minutes, probably a little bit less, shouldn't be much longer though.