a girl can squirt with anal too..
women have a sac similar to the prostrate located along their urethra tube (the tube piss comes from) basically all stimulation gets a girl to build up fluid in this sac jsut like a guy builds up fluid for cuming.
you can acheive this squirting in multiple ways.
1. repeated multiple orgasms in succession then continuing with stimulation until she literally cant hold it in. (stimulation anywhere, the clit, the g-spot, the vaginal opening, anal sex... doesnt really matter)
2. bringing her to the moment right before climax repeatedly (this makes her build fluid) each time you stop the fluid stays there, but when you restart stimulation she starts making more fluid. the more she has, the harder it is to hold in resulting in an intense climax where she cant hold it it.
3. massaging the g-spot, which is actually massaging the sac where the fluid builds. you can do this vaginally or anally, just like you can make a man cum by massaging his prostrate anally.
4. alternately you can give her multiple orgasms in any way you please, then press a finger or two, a fist, a vibrator, or other hard object on the g-spot and the pressure will force it out.
make sure she pees before you get started, build her up slowly or quickly. if she feels like she has to piss really bad, dont let her go, thats her body trying to relieve this fluid.