How Much Priming Sugar Needed?

I have one gallon of hard cider.

Five 22 oz bombers.

A couple of pounds of dextrose.

Ultimately, I'm guessing I'd just like to load the bombers with the dextrose and cap them.

How much priming sugar should I use per bottle?

Or..if that is not the preferred method by the advice given, how much priming sugar should be boiled in how much water then added to the cider when racking to the bottling vessel?

1oz of sugar per gallon of cider is the general rule.

Add 1 oz of sugar to just enough water to dissolve it, should be less then 1/2 or 1/3 of a cup of water. Though that into your bottling bucket, and then rack your cider on top of that. The racking with provide enough agitation to mix in the sugar. Then go ahead and bottle from there.

Thank you both. I appreciate it!

Assuming 1 oz sugar per gallon to prime, how much head space should I leave when final racking into 500ml and 750ml flip-top bottles? With too little head space, it seems the pressure could really build up.

--SiletzSpey