Typically a prestain treatment to reduce botching is a very thinned down shellac, on the order of 1/4 to 1/2 pound cut. They work by brushing on an excess and then quickly wiping off the excess after some number of seconds. What this does is help to clog the pores in areas that are highly absorbent (as they absorb more of the shellac) which is what causes the botching -- essentially much the same basis as wipe-on stains where the more absorbent areas absorb more stain and thus become darker than those areas that absorbed less. Afterwards you apply the regular stain treatment in much the same way, brushing on an excess then wiping it all off quickly after some seconds delay.
There is, however, a price to using prestain blotch treatments and that is a reduction in stain color intensity. This occurs because all areas of the board are at least partially clogged by the shellac prestain treatment, reducing the amount of stain that gets absorbed into the wood. It does greatly reduce botching but your finished intensity will not be nearly as dark as if you had used straight stain. The lighter stain does not necessarily look bad at all, but it may not be the intensity you might have expected and may not match other pieces you have made and finished with the same stain minus the pretreatment.
You our can potentially compensate for such in a number of ways if the result is not to your liking. You can use dye-based gel coat stains over top to help darken the piece. You can also add dye to your clear coat finish if using finishes like polyurethane or polycryllic to help intensify the coloration of your underlying stain. You can also try skipping the prestain treatment altogether and apply your stain in a highly controlled manner using a spray gun so that you can tightly control how much excess stain is available so that highly absorbent areas are limited to absorbing no more stain (i.e. starve the most highly absorbent areas that tend to blotch most objectionably) than the more absorbent rings so that all are of similar intensity and you can slowly build it up in multiple applications until you achieve a desired intensity, even choosing which areas will receive more or less stain if need be, which may reduce the intensity of botching to more acceptable levels (similar to dye application using a spray gun). Additionally, you may wish to consider stopping a little earlier in your sanding schedule as a coarser final grit leaves behind deeper scratches which can trap more stain and help to darken to wood versus sanding to a finer grit.
But most importantly of all, use your leftover scrap wood to test all your proposed finish schedules prior to applying such to your actual project. When you think you have found the best schedule for your project, try that finish schedule on a much larger piece of scrap sanded to the same final grit as your project (final grit heavily influences staining intensity) -- one that you know will produce blotching -- to verify that the effect you observed on the smaller scrap behaves precisely as expected on a larger scale where there is more variety in the grain patterns. To help identify a piece of scratch that should produce blotching pour denatured alcohol or mineral spirits on the board and quickly work in the alcohol or mineral spirits -- more highly absorbent areas will look darker in color (you could also use water, but will need resanding afterwards), then allow the board to dry before continuing. Only when you are fully satisfied should you apply your finish to your project and by then you should have much greater confidence in the process since you tested your finishing schedule before hand.
I'n sure you will get some even better advice from some of our finishing experts shortly.
