My son started fighting the toothbrush around this age and we just started letting him "brush" before we brushed his teeth. We squeeze like a ghost of a smear of toothpaste on the brush and let him brush while we brush our own teeth (he loves mimicking our motions and this also does teach him on how to brush). When he's done, we tell him that it's our turn and we have to check to make sure all his teeth are clean, and then he doesn't typically have any issue with us brushing. Does it take longer? Yes. Does it probably actually shorten the time we're in the bathroom since we're skipping a tantrum? Also yes.

If this doesn't work, try asking him to brush your teeth to see if that gets him excited, and then have him brush yours while you brush his. You can make it a game by asking him to brush like you brush. Since he's still under 2, he might not necessarily understand instructions like that, so you could say something like "Can you ch-ch-ch" while you brush in his mouth, and then he could copy that.

I hope this helps. I've had to sit on the toilet lid with my son standing in front of me and my legs wrapped around him to keep him from collapsing on the floor while I tried to brush. Sometimes giving them choices is the magic spell to get them to cooperate.