There are a lot of different resists, and the problem with all of them is that they either wash out too easily, and thus come out in the dyebath or the soda ash presoak, or they are difficult to remove.
The ones that wash out too easily can be used without the soda ash presoak, preferably by adding soda ash to the dye itself and lightly spraying it on with a hand spray bottle. These include all of the water-soluble resists, such as Presist, Silk-paint brand water-soluble resist, aqua guttas, etc. I learned this the hard way when I tried combining DEKA silk resist with direct Procion MX dye application, ten years ago.
Elmer's Blue Glue Gel, which you can often find in the local drug store or grocery store, can be used as a resist. The bottle makes a handy applicator. In
LWI, the glue may transfer to an adjacent section of fabric, whether placed face-to-face with it or by bleeding right through the back of the layer of fabric to which you've applied the glue. Do NOT use white glue: use only the blue Elmer's Washable School Gel. It can be difficult to get out; soak it for a while in cool water before washing in hot water, and it should all wash out. Here's a link to a
page showing an example of a shirt that was dyed with LWI using Elmer's Washable Blue Glue Gel as a resist.
The best resist on cotton is wax, as it gives the best results, but only if you get it hot enough (230°F), without risking fire with hotter temperatures, and use good ventilation so your lungs are not damaged by the fumes. Wax that is not hot enough will not penetrate the fabric well enough to work, but the dangers are obvious and real. You can use beeswax or a mixture of beeswax and paraffin wax. The problem then is getting the wax out of the fabric. Some people find that their local dry cleaners can remove wax; mine do NOT, and leave me with a nicely dry-cleaned item that is still full of hard wax. I use a large pot to boil out my wax, with a bit of liquid soap (not detergent) in the water, letting the wax harden on top as the water cools, before removing the fabric from the water. I do not like using an iron to remove wax.
Some dyers are using soy wax, with different results. Some like it and get good results; others find that it does not work. I have not tried it yet. I believe that even at best it is less water-resistant than real wax, so keep that in mind and avoid lengthy dye baths. If you try soy wax, be sure to get the hardest type, the pillar candle wax, which is the type that the dye suppliers such as Dharma and ProChem sell. It can be washed out with hot tap water (140°F).
Paula