First empty your bottle of red glitter glue into a bowl and mix in your water. Adding water is optional but it will make your slime stretchier.
Now mix in your baking soda.
Now add your 4 cups of shaving cream in and mix. This is where you'll need to add more red food coloring. The food coloring can stain so be sure to use a spoon for mixing and cover any surfaces to protect from staining. You'll need to add a lot of food coloring to get it red since the shaving cream is white. Also note that mixing with your hands you will get slightly stained from the red but it can be easily washed off.
Now slowly mix in your contact lens solution. If you add too much in, it will make your slime hard and not as stretchy. We like to add just a teaspoon at a time and mix until you're satisfied that the slime is not too sticky.
Now knead, knead, knead while continuing to add in your contact solution a teaspoon at a time. If this is your first time making slime, you'll be surprised how much you need to knead and mix the slime before it's a good consistency. This is normal. Keep mixing and slowly add in more contact solution.
At this point you can see how your slime consistency has turned out. If it's too sticky, add a bit more contact solution. If it's not fluffy enough, you can add another cup of shaving cream and work it into the slime. If you're still finding it sticky you can use some hand lotion on your hands while you're mixing and kneading it.