Probably both, but hard to say since you don’t say what you’re currently doing. I do along the lines of:
- Take off tyre
- Collect sealant
- Wipe area dry
- Fully dry area with heat gun
- Very lightly sand area where patch will go
- Wipe area with alcohol
- Apply vulcanising solution
- Wait for solution to dry*
- Apply patch
- Run over patch, especially edges, with a tyre lever
- Put in vice with rubber jaws fitted, tighten and leave overnight
This has never failed aside from an optimistic experiment trying to patch a 1" tear in a sidewall!
*or use my favourite trick of setting the carrier in the solution alight, blowing it out and repeating until it’s all gone. Bonus of this is it warms the area which may help the patch adhesion, plus you get to play with fire!
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That’s a pretty good process summary. Here are my variations/notes:
- I’ve never used a heat gun and I don’t think I usually use alcohol, but both seem like decent ideas.
- I use the sandpaper or abrasive metal thing that comes in the patch kit to really rough up the area around the puncture site. This is basically what the alcohol clean does but has the added bonus of giving some extra texture for adherence. In contrast, the argument in favor of alcohol is that tubeless tires tend to have a much thinner butyl layer than an old fashioned inner tube, so sandpaper runs the risk of actually taking parts of that layer off completely. However you do it, you need 100% clean, raw butyl/rubber lining with no coating of anything at all on it.
- FYI setting the cement on fire was a normal requirement of the glue and patch process at one point. I think modern vulcanising cement has been reformulated so this is no longer necessary. I’ve never really looked into the facts because the fire version was gone before I ever started cycling seriously.
- Number one issue in my personal learning curve was an assumption that you wanted tacky cement rather than completely dry (because how else will it bond?). But that’s not true - it’s more like spray contact adhesive and works way better if it is dry before applying the patch.
- My ‘applying pressure’ technique is to mount the tire with a tube in it at the max pressure I’m willing to take it to and leave it overnight. However you do this, the ‘overnight’ bit is important because the term ‘vulcanising’ means that there’s actually a chemical reaction happening where the two bits of rubber are bonded/welded together permanently. It’s not glue, it is a permanent bond. It takes 12-24 hours for this to happen and you need really firm even pressure over the entire surface of the patch for that full duration, especially at all of the edges.
- Always prep/sand/clean a bigger area than you think you’ll need, and it’s better to put too much vulcanising solution rather than too little - only drawback is it will take longer to dry.
- Don’t bother taking the clear plastic backer off the top of the patch when you’re done - It’s not a problem to leave it there and then you avoid the risk of pulling up the edges of the patch when you remove it. It disintegrates with the friction of riding in the next ~50 miles with tubes. With tubeless the only real risk is it becomes an anchor point for stanimals so you might have to remove it during your next sealant top up.
These are good tips if you’re having issues, but in most cases you don’t need to be that clinical - I’ve literally just finished patching the inner tube on a friend’s step-through city bike and all I used was sandpaper, cement, waited til it dried, pressed it firm between my thumbs for a minute or so, and then reinstalled it and reinflated. Assuming that ~40psi is the right balance between applying pressure to the patch from inside the tire and the air inside the tube trying to escape through the un-cured patch, then by this afternoon it will be far enough along in the process that we’ll know we’re going to get a permanent fix.
I actually do very lightly sand before wiping clean with alcohol, good reminder - I’ll update my process 
I agree also with how counterintuitive it is to have ‘glue’ that you let get dry before sticking something! In most other cases that would mean you’ve left it too late 
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