This will all sound way more complicated then it is. I did a yellow/coral/red gradient nail with a make-up sponge. Then I used a dotting tool to add black over the top to make flames.
Step 1- Base coat. I used Essie All in One Base.
Step 2- One coat of white or milky colored ridge filler. Most yellows take several coats. Over a white polish, you need less coats of yellow polish. I used Sally Hansen Whirlwind White.
Step 4- Add a 2nd coat of yellow halfway up the nail.
Step 5- My only polish color that didn't have shimmer was the yellow. So I added a coat of Essie Pure Pearlfection halfway up the nail over the part that will remain yellow. If none of your polish colors have shimmer, wait until you are done with the yellow/orange/red gradient, and then add a coat of shimmer. You will want the entire gradient to have shimmer. This part will eventually become the fire.
Step 8- Paint squiggles on the nail with a black polish. I used Wet n Wild Black Cream. Ideally you want a cream finish to contrast with the shimmery fire gradient. You can either use a dotting tool or a nail art brush to paint the squiggles. I used a dotting tool. When I was trying this out over an old manicure a few weeks ago, I used a art brush and that worked fine too.
Step 9- Paint black in a fine line along the edges and cuticle of the nail using either a dotting tool or a nail art brush. Paint closed any areas at the top (by cuticle) that seem like they should be connected. I connected a few too many squiggles. The video shows how to do step 8 and 9 and shows an alternate way to do a fire nail.
Step 10- Top coat. I used Seche Vite.
May the odds be ever in your favor.