Well, fillers are fine for a lot of folks, but I just find them a bother. Since you are planning on around 25grs, I might assume you are going to shoot CAS with your Remmie. 777 is about 10% higher in power than in other powders and what you want to load should give you some good recoil and feel stout.
One thing available is the stand with ram that you can actually load your cylinders out of the gun. With one of those devices you can simply load and ram a ball onto the powder. For consistency you want to have no air space above the powder. Lot's of folks will tell you to use the wonder wad or put some grease over the ball to prevent flashover and then a chainfire. I never do and since most chainfires start at the nipple end and your powder will be really down in the cylinders, you might not bother with the mess either. 777 burns really clean and lube isn't that important with the powder either. A good fitting ball like 454 diameter will shave a nice ring of lead when rammed. That indicates a good fit and seal. The wonder wad will give you a lot more security and help lube and keep the barrel free from fouling. They are however on the pricey side.
One thing folks do to download C&Bs is use a 38 cal bullet. You ram the ball as far as you can with the rammer and then place a 358 dia bullet onto the ball and ram again and shake the bullet out and go on to the next cylinder. There are lots of ways to do things. I know a good pard that loads only 15 grains of 777 in rooger ROAs. He has been doing it since 777 came out 3 or 4 years ago, with excellent results at CAS distances.
Your load is just what I would use, since my normal load is 30grs with true black powder and even APP. I shoot 777, but only in my long range calibers of 38-55 and 45-70. I didn't care for it in pistols although it shot fine, cleaned up good and did not foul. There are a lot of choices and ways to go when shooting C&B. :-)
