Need your help on Whoa issue

Thinking of buying this little guy to ride with my TW. Our other horses are QH's which are great but no so great to ride with a TW.
Rocket, the horse in question is 1/2 Icelandic 1/4 Arab and 1/4 TW. A horsey friend down the rode has him. This horsey friend breaks horses for another friend/breeder. This friend calls what he does "training" but I question this. Anyway Rocket was broke at 2.5 and sold to a young girl 14 who apparently abandonded him at a barn for almost 3 yrs. When the BO went out of business recently my friend found out about it and had the breeder buy him back. Anyway I rode him the other day with this friends horses and he did pretty well. I then rode him Sunday and my friend Kim rode my TW. Since he was not with his herd he called out for them a lot and kept trying to turn for home. Not a problem but when we stopped he also did not want to stand still. Not being a "trainer" when he would start to walk off I would turn him in small circles for a bit and then stop and let him try again to stand. HOnestly it really did not work however I did not work him hard since we were standing in a rock creek bed. Later when we loped and Kim went by us on my TW and even when she stopped I had a hard time getting Rocket to stop. I think he does not really understand whoa and needs some work. I have seen this friend "train" horses and there is no ground work at all. Just force the bridle on and ride off following the other horses. I think the only reason he has not gotten hurt bad is because he normally breaks Icelandics and they have a real kind nature.
Anyway when we got back and the friend asked how he did I told him and he hit the ceiling saying that I was letting the horse move and I should have jerked on him with the bit enough to make him stand. He said that by doing circles I was letting the horses get away it and it will just be worse next time.He went on to tell me that I am ridiculous about "not getting in their mouth" and so on. As you can tell we have some very different views but since I am by no means a "trainer" I would really like your opinions.
Thank you so much.

Jerking hard on the bit doesn't do anything except make a hard mouth. I do agree that the circles may have not been the best thing, but that doesn't make you a horrible rider. Different strokes for different folks! I have a TB, who are notoriously very antsy/impatient and usually what I do is the half halt, and if he continues on then I back him up more steps than he took (if he took 3 steps forward, we take 4 back, etc). However, when I'm on the ground, I do usually turn him in circles.

Number 1: whoever told you that you were wrong to make him do circles is wrong! They need to know that you can not pull on their mouth like that because then they will dredd the bit everytime making it harder for you to get the bridle on (i dont blame the horse tho). What you did was right! You want to make it as pleasureable for both you and the horse so that the next time you go out he remembers that the last time wasnt too bad. Since you said the "trainer" did no ground work with him, than that is something you NEED to do. Groundwork is critical, it helps you and your horse commuicate like never before. If you want tips on what to do such as groundwork let me know. I hope this helps a little bit. GOOD LUCK!

So you need to teach Whoa - start at the walk (no rider) with a leadline standing at the horses left shouder, step forward. Horse should immediately step forward with you. then say WHOA while stopping. If horse does not stop immediately snap the lead down (1 quick jerk) and repeat Whoa. Do this in a place where he normally would stop without a problem.

Once he does that (i.e. reacts immediately to YOU) then migrate from where he'll willingly stop to places where he is more easily distracted. Stop/walk MANY times with a few steps in between. Gradually add more walk steps but remember - he must ALWAYS halt when you halt.

Sequence is you halt, then (if needed) you say WHOA then (if needed) you snap o=down on lead. Idea is he halts WHEN you do and at (or slightly behind) your shoulder - NOT in front of your shoulder.

If he stops in front of you shoulder step in front of him and make him back up (AT least TWO steps) immediately.

OK - when you've gotten his respect on the ground start it from his back. This time when you sit deeply in the saddle press straight down with both stirrups then say WHOA. Do NOT lean forward or back - rider MUST be straight up and down (think of standing in the stirrups and that will place your body and legs in the proper position). Use WHOA if he's slow to respond to halting from your riding.

This will take a while as you're etaching him - you didn't learn to read in 1 day and he won't learn to perform a perfect halt in 1 day either - it's repitition so you MUST be consistent EVERY time you ride him.

When you have him halting from the walk, move into the halt from the trot. Same thing as from the walk

Thank you so much for your responses and advise. I didnt think jerking on his mouth was going to help anything and now you have given me some tools.
Thanks again, I really appreciate it and so will Rocket..

I wouldnt ever suggest jerking on the bit. Like one poster said, back them up to either be in the spot they were before or one step further back. It shouldnt be a "you moved so now I'll rip at your mouth" or anything, moreso a "we start from here, not over there." And when you back up, don't be rough, all you need is to hold the rein and use a little leg. No pulling required, just holding to prevent him from going forward.