Hello LadyG! I'm sorry to hear of your troubles, but please know that you're not alone. I'm similarly blessed with severe RA and originally had issues myself with removing the slide of my Glocks using the factory slide stop, which just didn't offer me enough real estate for my weak fingers to engage, even when trying to operate it one side at a time.
I knew that I would need an extended slide stop, and found both straight and angled varieties available. Through observation I believed that the angled extended slide stop variety like the one shown below would work best for me, and it did, so now each of my 3 Glocks have them installed:
The above is available from RockYourGlock for $11.95:
http://www.rockyourglock.com/custom/RYG-ESL.htm
Please note that other manufacturers offer similar items for less money, so shop around at Glockmeister, Lone Wolf Distributors, etc. if you like to engage in comparative shopping
I also found that in regards to pulling the slide back slightly prior to operating the slide lock, that I had problems doing so with the generally prescribed method shown below from a previous post:
The above method requires the use of too much finger strength for me to use and maintain, which also then due to the position of my left in relation to my right hand makes operating the slide lock awkward, so through my own experimentation I found that the method below works much easier for me:
In the above image I'm simply squeezing my left hand as if making a fist, which places the pistol in a position that better allows me the means to then very comfortably operate the slide lock with my right hand. This in combination with the angled slide lock makes disassembly of my Glocks a much easier experience.
I've thankfully managed to overcome my difficulties with this issue, and I hope you'll be successful too
