@MonkeyJenga just sent you a PM with details on that group.
I think that could work with Open Progress. I've definitely done it before (again, so long as I have 1 trainer for about every 3 newbies) on zoom and it worked out. Resistance Labs definitely doesn't require use of their Slack. Some people use it, but it's a bit of a ghost town and if people have questions that they ask there, I'm not sure that they get answers as quickly as they do on, e.g. OP's Slack, where they have moderators for like 8-12 hours a day staffing the channel.
I think your plan sounds very fair and good re: Mobilize. Re: setting up texting for your sponsored candidate, I'd recommend Red2Blue or Open Progress. They run everything for you, which is great because then you don't have to learn to run the texting software yourself as an admin, and they have a lot of scripting expertise and other stuff that you can take advantage of. Open Progress owns TextOut (their software to send texts) and I'm not sure how their pricing works, if the cost of TextOut includes the cost of their services or what. You can learn more here:
https://www.textout.io/Red2Blue is all volunteer and their services are free, but currently they only work with one texting software, ThruText, and they can get the candidate a discount through a partnership with them. They specialize in state legislature texting and other down ballot races like county commissioners and such. This is where I refer the candidates I work with. Check them out here:
https://www.red2blue.org/for-candidates-overviewI suspect (but don't *know*) that if you want to reserve the texting for you and your fellow volunteers to actually do the sending, that OP/TextOut might be a better avenue? I think I've seen that you can have it not go through OP itself, where their volunteers would send the texts. Red2Blue that's not really possible. They have their vols send the texts. Of course, your people can get trained up with them and become "their vols" too. They can then show up when the texting is going to happen and put in requests for batches ahead of time, so it can still work for you all to do it, it's just not really *reserved* for your own volunteers.
Hope that helps!