Non-verbal 2yr old

Hi all. I’m really stuck trying to introduce potty training to my 2yr8month son. He’s mostly non-verbal (Mumma, dadda, nanna, etc.). He definitely understands what I’m meaning by “let’s try doing our wee on the potty!” as he will visibly hold his wee in, then pee in the house/garden and say “uh oh”. We also have an 8 month old who is EBF so it’s slightly tricky sometimes to be able to follow him around. Is there any visual aids I can maybe use to encourage him? I bought hot wheels to give him as a “well done” for any wees or poos, but he didn’t seem fussed even still. Thanks in advance!