I think you should focus on explaining that lemmygrad (or hexbear) as a whole is where they can be safe like on r/thedeprogram, except they won’t get their accounts banned by admins. I think you should probably explain the application process to make it less intimidating (i.e. you don’t need to give some super complicated answer, one sentence for each question will suffice and the admins are unlikely to reject you unless you outright say “I hate communism” or are a patsoc)
Make a persuasion post in general for why lemmy can be a superior reddit alternative (different sorting algorithms, lack of corporate control and data harvesting, responsive devs who are comrades! Etc.) Point out that you are likely to get high engagement on posts here even with the small comms because the atmosphere is so much friendlier. Are all the other mods from r/thedeprogram here on lemmygrad? I would suggest getting them on board here if you can
Could be annoying, but maybe have the automod respond to any post containing the word “reddit”?
ETA: also, should have mentioned lemmygrad on the rule crackdown post. Another thing, is to let people know that there are actually apps you can use now, and let them know what their names are