Just do not use regular masking tape, it leaves a messy sticky residue behind!
The purple water erase pens work well, so does chalk, ceramic pencil, the blue air erase pens...there are lots of options that work. For years I stuck with a regular mechanical pencil. I never had a problem removing marks. I have the past few years started using others too. The keys to success are:
1. Prewash your fabric ( some products just don't work well on fabrics that still have the sizing, chemicals in them.)
2. Read the instructions on the package! Some markers will come right out unless you touch them with an iron & heat- set that ink- then its permanent. Some markers disappear with an iron, but don't get it wet.- read the instructions, know what you are using.... Everything has its own method that works.
And lastly, but Most Important...
3. Always,Always, Always test your choice to make sure it comes out before you mark a whole quilt!