You can stuff a rag in the skimmer to slow down any flow. If you use the blue PVC glue any water left in the pipe won't hurt anything. You can wipe the primmer on everything before cutting pipe. Don't worry if you mis some places with the primmer. I've done sprinkler repairs where water was gushing out of pipes and after adding a splice with blue glue - no more problems.
Good Luck
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