Ok, here is how I do them, others might differ.
1.) Wash the parts in a diswashing soap solution, keep an old toothbrush handy.
2.) You can use CA or Epoxy glue (5 min. setting time will do, 2.min for non weight bearing joints)
3.) Primers there is a wide range out there and you will get as many recommendation as replies(most likely)
4.) Cleanup depends, if the casting sprue is still attached, you can cut it careful off with nipper, cleanup with Hobby knfie and sandpaper is recommended. Parts from a 2-part mold will have a moldline, carefull when cleaning that.
5.) Small Rein parts need to handled careful as the resin can snap and you will end up with multiple pieces.
6.) Resin can be heated, the part will than need to be fixed in position to correct any bends/warps and be left to cool. Might take 2 or 3 times to get it right.
Hope this helps.