Well, according to the newz story I linked, they had only raised about $90K to finance this expedition.  That does not indicate a huge  following or turnout.  It would be very expensive for an independent trucker to do the wwhole trip, both in the cost of fuel + the time lost you could be pulling freight.  No trucking company would let a driver take the trip in a company vehicle.

However, they aren't only recruiting truckers, they want biker clubs like the Hells Angels and retired cops to take the trip as part of the convoy.  These folks have the time and the bikers go out together for club joyrides anyhow, so that's their base.

Far as the truckers go, they are driving the I-10, and once on the road they'll pick up truckers driving the route anyhow for at least part of the trip.  Anybody who has a cross country freight load booked during that week usually has a day or 2 of flexibility on the delivery date, so if they are real supporters of anti-immigration they might be able to do most of the route.

The big question is how many drivers on the I-10 they can pull into the convoy along the route.  They'll all be chatting on the CB radios as they go, and will recruit along the way.  If they are smart, they'll run an advance team about 12 hours before the main convoy starts and hit all the truckstops along the I-10 passing out flyers to idle truckers in the parking lots.

I doubt it will draw in that many, but I could see upwards of 500 vehicles starting out and maybe a couple of thousand at the end.  There's also the significant chance a counter protest group will tag along, including agent provocateurs to make trouble along the way.  If violence breaks out, that would get them newz coverage, so that might even be planned secretly.

They should be getting on the road soon, so just have to search the newz to see if anything turns up.

RE